a: \(\left(-\dfrac{2}{3}\right)^2\cdot\dfrac{3}{5}-\dfrac{7}{18}\cdot\dfrac{3}{5}\)
\(=\dfrac{3}{5}\left(\dfrac{4}{9}-\dfrac{7}{18}\right)\)
\(=\dfrac{3}{5}\cdot\left(\dfrac{8}{18}-\dfrac{7}{18}\right)=\dfrac{3}{5}\cdot\dfrac{1}{18}=\dfrac{1}{6\cdot5}=\dfrac{1}{30}\)
b: \(\left(-18\right)^4:9^4+\left(-\dfrac{1}{2}\right)^3-\left(-2025\right)^0+3\dfrac{1}{8}\)
\(=\left(-\dfrac{18}{9}\right)^4+\dfrac{-1}{8}-1+3+\dfrac{1}{8}\)
\(=\left(-2\right)^4+\left(-\dfrac{1}{8}+\dfrac{1}{8}\right)+\left(3-1\right)\)
=16+2=18
c: \(\dfrac{9}{\sqrt{\left(-11\right)^2}}-\left|\sqrt{0,04}-\sqrt{7}\right|-\left(20\dfrac{9}{11}-\sqrt{7}+1,7\right)\)
\(=\dfrac{9}{11}-\left|0,2-\sqrt{7}\right|-\left(20+\dfrac{9}{11}-\sqrt{7}+1,7\right)\)
\(=\dfrac{9}{11}-\left(\sqrt{7}-0,2\right)-20-\dfrac{9}{11}+\sqrt{7}-1,7\)
\(=\left(\dfrac{9}{11}-\dfrac{9}{11}\right)+\left(-\sqrt[]{7}+\sqrt{7}\right)+\left(0,2-20-1,7\right)\)
\(=0+0+\left(-1,5-20\right)=-21,5\)
`a, ((-2)/3)^2 . 3/5 - 7/15 . 3/5`
`= 4/9 . 3/5 - 7/15 . 3/5`
`= 3/5 . (4/9 - 7/15)`
`= 3/5 . (-1)/45`
`= -1/75`
`b, (-18)^4 : 9^4 + (-1/2)^3 - (-2025)^0 + 3 1/8`
`= (-2)^4 - 1/8 - 1 + 25/8`
`= (16 - 1) + (-1/8 + 25/8)`
`= 15 + 3`
`=18`
mọi người giúp mình với ạ, mai mình đi thi thi. Cảm ơn mọi người nhiều 
