Đáp án:
`d) 2 × x + 8 × x - 7 × x = 135`
`(2 + 8 - 7)× x = 135`
`3 × x = 135`
`x = 135 : 3`
`x = 45`
`e) 2 × x + 7 × x - 5 × x = 76`
`(2 + 7 - 5) × x = 76`
`4 × x = 76`
`x = 76 : 4`
`x = 19`
`f) x : 0,1 + x : 0,25 - 35 = 35`
`x : 1/10 + x : 1/4 = 35 + 35`
`x × 10 + x × 4 = 70`
`x × (10 + 4) = 70`
`x × 14 = 70`
`x = 70 : 14`
`x = 5`