a)  20 : 2 2 − 5 9 : 5 8 = 5 − 5 = 0

b)  ( 5 19 : 5 17 − 4 ) : 7 0 = ( 5 2 − 4 ) : 1 = 21

c)  295 − ( 31 − 2 2 .5 ) 2 = 295 − 11 2 = 174

a 20:2^2 -5^9:5^8

= 20:4 - 5^1

=5-5

=0

a)  20 : 2 2 − 5 9 : 5 8 = 5 − 5 = 0.

b)  ( 5 19 : 5 17 − 4 ) : 7 0 = ( 5 2 − 4 ) : 1 = 21.

c)  295 − ( 31 − 2 2 .5 ) 2 = 295 − 11 2 = 174.

;)

\(48\div4+3^9\div3^7+5^0\)

\(=12+9+1\)

\(=22\)

\(\left(5^{19}\div5^{17}+3\right)\div7\)

\(=\left(25+3\right)\div7\)

\(=28\div7\)

\(=4\)

\(295-\left(32-2^2\times5\right)^2\)

\(=295-144\)

\(=151\)

\(6^2\div9+50\times2-3^3\times3\)

\(=36\div9+100-27\)

\(=4+100-27\)

\(=100-27\)

\(=73\)

\(48:4+3^9:3^7+5^0\)

\(=12+3^{9-7}+1\)

\(=12+9+1\)

\(=22\)

\(\left(5^{19}:5^{17}+3\right):7\)

\(=\left(5^{19-17}+3\right):7\)

\(=\left(5^2+3\right):7\)

\(=\left(25+3\right):7\)

\(=28:7\)

\(=4\)

\(295-\left(31-2^2\cdot5\right)^2\)

\(=295-\left(31-4\cdot5\right)^2\)

\(=295-\left(31-20\right)^2\)

\(=295-11^2\)

\(=295-121\)

\(=174\)

\(6^2:9+50\cdot2-3^3\cdot3\)

\(=36:9+50\cdot2-3^4\)

\(=4+100-81\)

\(=23\)

\(48:4+3^9:3^7+5^0=12+3^2+1=12+9+1=22\)

\(\left(5^{19}:5^{17}+3\right):7=\left(5^2+3\right):7=\left(25+3\right):7=28:7=4\)

\(295-\left(31-2^2.5^2\right)=295-\left(31-10^2\right)=295-\left(31-100\right)=295-\left(-69\right)=364\)

\(6^2:9+50.2-3^3.3=36:9+100-3^2=4+100-9=95\)

a. 75+58.50 - 58.25

= 78 + 58 . ( 50 - 25)

= 78 + 58 . 25 

= 78 + 1450

= 1528

b. 20 : 2² - 5⁹ : 5⁸

= 20 : 4 - 5

= 5 - 5

= 0

c. (5¹⁹ :5¹⁷ - 4 ):7

= ( 5² -4 ) : 7

= (25 - 4 ) : 7

= 21 : 7

= 3

d. 84:4 +3⁹:3⁷

= 21 + 3²

= 21 + 9

= 30

e. 295 -  ( 31 - 2².5 )²

= 295 - ( 31 - 4 . 5 )²

= 295 - ( 31 - 20)²

=295 - 11 ²

= 295 - 121

=174

4: \(=\dfrac{2+3}{7}+\dfrac{1+6}{9}-\dfrac{5}{6}=\dfrac{5}{7}+\dfrac{7}{9}-\dfrac{5}{6}=\dfrac{83}{126}\)

5: \(=\dfrac{-5-2}{7}+\dfrac{3+1}{4}-\dfrac{1}{5}=-\dfrac{1}{5}\)

6: \(=\dfrac{-3-28}{31}+\dfrac{-6-1}{17}+\dfrac{1-5}{25}=-1-\dfrac{7}{17}-\dfrac{4}{25}=-\dfrac{668}{425}\)

4. \(\dfrac{2}{7}+\dfrac{1}{9}+\dfrac{3}{7}+\dfrac{5}{9}+\dfrac{-5}{6}\)

\(=\left(\dfrac{2}{7}+\dfrac{3}{7}\right)+\left(\dfrac{1}{9}+\dfrac{5}{9}\right)+\dfrac{-5}{6}\)

\(=\dfrac{5}{7}+\dfrac{2}{3}+\dfrac{-5}{6}\)

\(=\dfrac{30+28+\left(-35\right)}{42}=\dfrac{23}{42}\)
 

5. \(\dfrac{-5}{7}+\dfrac{3}{4}+\dfrac{-1}{5}+\dfrac{-2}{7}+\dfrac{1}{4}\)

\(=\left(\dfrac{-5}{7}+\dfrac{-2}{7}\right)+\left(\dfrac{3}{4}+\dfrac{1}{4}\right)+\dfrac{-1}{5}\)

\(=\dfrac{-7}{7}+\dfrac{4}{4}+\dfrac{-1}{5}\)

\(=-1+1+\dfrac{-1}{5}\)

\(=-\dfrac{1}{5}\)
 

6. \(\dfrac{-3}{31}+\dfrac{-6}{17}+\dfrac{1}{25}+\dfrac{-28}{31}+\dfrac{-1}{17}+\dfrac{-1}{5}\)

\(=\left(\dfrac{-3}{31}+\dfrac{-28}{31}\right)+\left(\dfrac{-6}{17}+\dfrac{-1}{17}\right)+\dfrac{1}{25}+\dfrac{-1}{5}\)

\(=\dfrac{-31}{31}+\dfrac{-7}{17}+\dfrac{1}{25}+\dfrac{-1}{5}\)

\(=-1+\dfrac{-7}{17}+\dfrac{1}{25}+\dfrac{-1}{5}\)

\(=\dfrac{-425+\left(-175\right)+17+\left(-85\right)}{425}=\dfrac{-668}{425}\)

a) -72.17+72.31 - 36 . 228

 = -72.17 + 72. 31 - 36.2.114

 = -72 .17 + 72 . 31 -72 . 114

 = -72. ( 17-31+114)

 = -72 . 100

 = -7200

b) ..........

 = -7 . ( 16-36.9) -(-125) 

 = -7 . ( 16-324) +125

 =-7 . ( -308) +125

 = 2156+125

 = 2281

$a)$

$-72.17+72.31-36.228$

$=-72.17+72.31-36.2.114$

$=-72.17+72.31-72.114$

$=72(31-17-114)$

$=72.(-100)=-7200$

$b)$$-7.[{(-2)}^4+(-36):(-3^2)]-{(-5)}^3$

$=-7.[16-36:(-9)]+125$