Đáp án:
Giải thích các bước giải:
2.
`( 1/2 + 4/5 ) - ( 3/5 - 3/7 ) = 13/10 - 6/35 = 79/70`
`( 5/9 + 4/9 ) ×1/2 = 1 × 1/2 = 1/2 `
` 10/8 × 2/3 - 3/4 × 1/6 = 5/6 - 1/8 =17/24 `
`(2×9×5×7)/(6×7×3×8) = (2×9×5)/(6×3×8)=5/8`
`(7/6 - 1/3) : 4/5 = 5/6 : 4/5 = 25/24`
3.
` 4/5 × 3/x × 2/11 = 48/220 `
` 3/x = 48/220 : 2/11 : 4/5 `
` 3/x = 3/2 `
`x =2 `
` 4/3 : x/5 = 5/13 × 8/18`
` 4/3 : x/5 = 20/117`
` x/5 = 4/3 : 20/117`
`x/5=39/5 `
`x = 39`