a =  57/10

b = 12/5

c = 10/3

a) 57/10

b)12/5

c)10/3

57/10

12/5

10/3

5+ 5 + 5 + 5+ 5 + 5 +5+ 5 + 5 +5=5x10=50

25 + 25 + 25 + 25 + 25 + 25 +25 + 25=25x8=200

45 + 45 + 45 + 45 + 15 + 15 + 15 + 15=(45x4)+(15x4)=180+60=240

5+ 5 + 5 + 5+ 5 + 5 +5+ 5 + 5 +5
= 5 x 10
= 50

25 + 25 + 25 + 25 + 25 + 25 +25 + 25
= 25 x 8
= 200

45 + 45 + 45 + 45 + 15 + 15 + 15 + 15
= 45 x 4 + 15 x 4
= 180 + 60
= 240

2 + 4 + 6 + 8 + 10 + 12 + 14 + 16 + 18
= (2 + 18) + (4 + 16) + (8 + 12) + (6 + 14) + 10
= 20 + 20 + 20 + 20 + 10 
= 20 x 4 + 10
= 80 + 10
= 90 

125 + 125 + 125 + 125 - 25 - 25 - 25 - 25 
= 4 x (125 - 25) 
= 4 x 100 
= 400
(Tick cho mk pls ^^)

1) (-5) . (-8) - 45 . (-3) +(-6) . (-12)= 247

b) 6 . (-15) + (-8) . (-9) - 72 . (-2)= 126

c) (-15) . 4 - (-4) .16 - (-8) . 32 = 260

nhanh nhé

a, 1. \(\dfrac{2}{17}\)

2. \(22\)

3. 4

b,

1. \(\dfrac{8}{5}\)

2. \(\dfrac{176}{5}\)

3. \(\dfrac{28}{5}\)

4. \(\dfrac{3}{10}\)

5. \(\dfrac{163}{5}\)

6. \(\dfrac{9}{20}\)

a) \(\dfrac{12}{17}:6=\dfrac{12}{17}\cdot\dfrac{1}{6}=\dfrac{2}{17}\)

a) \(16:\dfrac{8}{11}=16\cdot\dfrac{11}{8}=22\)

a. 2227/3

b. 1/44

\(a\frac{2227}{3}\)

\(b\frac{1}{44}\)

\(8h+15'30''+45'+16'\)

\(=8h+15'+30''+45'+16'\)

\(=8h+\left(15'+45'+16'\right)+30''\)

\(=8h+\left(60'+16'\right)+30''\)

\(=8h+\left(1h+16'\right)+30''\)

\(=\left(8h+1h\right)+16'+30''\)

\(=9h+16'+30''\)

\(=9h16'30''\)

8 giờ + 15 phút 30 giây + 45 phút +16 phút 

= 9 giờ 30 giây

study well

$YOUTUBER$

= 9gio 30 giay

3)\(\dfrac{-41}{32}\left(\dfrac{15}{8}-\dfrac{16}{41}\right)+\dfrac{15}{8}\left(\dfrac{41}{32}-\dfrac{8}{3}\right)\)

=\(\dfrac{-41}{32}.\dfrac{15}{8}-\dfrac{-41}{32}.\dfrac{16}{41}+\dfrac{15}{8}.\dfrac{41}{32}-\dfrac{15}{8}.\dfrac{8}{3}\)

=\(\left(\dfrac{-41}{32}.\dfrac{15}{8}+\dfrac{15}{8}.\dfrac{41}{32}\right)+\dfrac{-16}{41}.\dfrac{-41}{32}-\dfrac{15}{8}.\dfrac{8}{3}\)

=\(0+\dfrac{1}{2}-5=\dfrac{-9}{2}\)

4)\(\dfrac{13}{29}\left(\dfrac{29}{5}-\dfrac{45}{8}\right)-\dfrac{45}{8}\left(\dfrac{9}{8}-\dfrac{13}{29}\right)\)

=\(\dfrac{13}{29}.\dfrac{29}{5}-\dfrac{45}{8}.\dfrac{13}{29}-\dfrac{45}{8}.\dfrac{9}{8}-\dfrac{45}{8}.\dfrac{13}{29}\)

=\(\left(\dfrac{45}{8}.\dfrac{13}{29}-\dfrac{45}{8}.\dfrac{13}{29}\right)-\dfrac{13}{29}.\dfrac{29}{5}-\dfrac{45}{8}.\dfrac{9}{8}\)

=\(0-\dfrac{13}{5}-\dfrac{405}{64}=\dfrac{-2857}{320}\)

14)

\(\left(27.45+27.55\right):\left(2+4+6+...+18\right)\)

\(=\left[27\left(45+55\right)\right]:\left[\frac{\left(18+2\right)9}{2}\right]\)

\(=\left(27.100\right):90\)

\(=2700:90\)

\(=30\)

15)

\(\left(26.180-26.12\right):\left(32-18+....+8-4\right)\) 

\(=26\left(180-12\right):\left(14+4+4+4+4+4+4+4\right)\)

\(=26.168:42\)

\(=84\)

Bài 2:

a: Ta có: \(2x+79=x+45\)

nên 2x-x=45-79

hay x=-24

b: Ta có: \(15-\left(x+7\right)=\left(x-8\right)+22\)

\(\Leftrightarrow8-x-x-14=0\)

\(\Leftrightarrow2x=22\)

hay x=11