`a, (5^2 +20:2^2):5`
`= (25 +20:4):5`
`= ( 25+5):5`
`= 30:5`
`= 6`
`b, (-1/4)^2 * (7/9) +1/16 * (-2/9)`
`= 1/16 * (7/9) +1/16 * (-2/9)`
`=1/16 * (7/9 + (-2)/9)`
`= 1/16* 5/9`
`= 5/144`
`c, 5/12 - (-1/4+ 5/12) : 7/6 -1`
`=5/12 - ( -3/12 +5/12) xx 6/7 -1`
`= 5/12 - 2/12 xx 6/7-1`
`= 5/12 - 1/6xx 6/7-1`
`= 5/12 - 6/42-1`
`= 5/12 - 1/7 -1`
`= 23/84-1`
`= -61/84`
a: \(\dfrac{5^2+20:2^2}{5}=\dfrac{25+20:4}{5}=\dfrac{25+5}{5}=\dfrac{30}{5}=6\)
b: \(\left(-\dfrac{1}{4}\right)^2\cdot\dfrac{7}{9}+\dfrac{1}{16}\cdot\dfrac{-2}{9}\)
\(=\dfrac{1}{16}\cdot\dfrac{7}{9}-\dfrac{1}{16}\cdot\dfrac{2}{9}\)
\(=\dfrac{1}{16}\left(\dfrac{7}{9}-\dfrac{2}{9}\right)=\dfrac{5}{9}\cdot\dfrac{1}{16}=\dfrac{5}{144}\)
e: \(\dfrac{5}{12}-\left(-\dfrac{1}{4}+\dfrac{5}{12}\right):\dfrac{7}{6}-1\)
\(=\dfrac{-7}{12}-\left(\dfrac{-3}{12}+\dfrac{5}{12}\right)\cdot\dfrac{6}{7}\)
\(=\dfrac{-7}{12}-\dfrac{1}{6}\cdot\dfrac{6}{7}=\dfrac{-7}{12}-\dfrac{1}{7}=\dfrac{-49-12}{84}=-\dfrac{61}{84}\)
