Đáp án:
Bài `1`
`a,`
`75% + 1,2 - 2 1/5 + 2016^0`
`= 3/4 + 6/5 - 11/5 + 1`
`= 39/20 - 11/5 + 1`
`= (-1)/4 + 1`
`= 3/4`
`b,`
`2 1/2 ÷ (5/2- 3 3/4) + ( (-1)/2)^2`
`= 5/2 ÷ (5/2 - 15/4) + 1/4`
`= 5/2 ÷ (-5)/4 + 1/4`
`= -2 + 1/4`
`= (-7)/4`
`c,`
`4/9 × 5/17 + 4/9 × 30/17 - 1/17 × 4/9`
`= 4/9 × (5/17 + 30/17 - 1/17)`
`= 4/9 × 2`
`= 8/9`
$\\$
Bài `2`
`a,`
`3x - 75%x = -1,2`
`-> (3 - 75%)x = -1,2`
`-> 9/4x = -1,2`
`-> x = -1,2 ÷ 9/4`
`-> x = -1,2 × 4/9`
`-> x =(-8)/15`
Vậy `x= (-8)/15`
`b,`
`|1/3x - 1/4| - 1/6 = 1/2`
`-> |1/3x - 1/4| = 1/2 + 1/6`
`-> |1/3x - 1/4| = 2/3`
`->` \(\left[ \begin{array}{l}\dfrac{1}{3}x-\dfrac{1}{4}=\dfrac{2}{3}\\ \dfrac{1}{3}x-\dfrac{1}{4}=\dfrac{-2}{3}\end{array} \right.\)
`->` \(\left[ \begin{array}{l}\dfrac{1}{3}x=\dfrac{2}{3}+\dfrac{1}{4}\\ \dfrac{1}{3}x=\dfrac{-2}{3}+\dfrac{1}{4}\end{array} \right.\)
`->` \(\left[ \begin{array}{l}\dfrac{1}{3}x=\dfrac{11}{12}\\ \dfrac{1}{3}x=\dfrac{-5}{12}\end{array} \right.\)
`->` \(\left[ \begin{array}{l}x=\dfrac{11}{12}÷\dfrac{1}{3}\\x=\dfrac{-5}{12}÷\dfrac{1}{3}\end{array} \right.\)
`->` \(\left[ \begin{array}{l}x=\dfrac{11}{4}\\x=\dfrac{-5}{4}\end{array} \right.\)
Vậy `x=11/4` hoặc `x=(-5)/4`
