$\text { Đáp án: }$
` a) `
` 1/2 . ( 2/9 + 3/7 – 5/27 ) `
` = 1/2 . 88/189 `
` = 44/189 `
` b) `
` ( –5/28 + 1,75 + 8/35 ) : ( –3 . 9/20) `
` = 9/5 : ( –27/20 ) `
` = 9/5 . ( –20/27 ) `
` = –4/3 `
` c) `
` 1/3 . 5/7 – 7/27 . 36/14 `
` = 5/21 – 2/3 `
` = –3/7 `
` d) `
` 70,5 – 528 : 15/2 `
` = 70,5 – 528 . 2/15 `
` = 70,5 – 70,4 `
` = 0,1 `