`f)`
`3/2 × x - 2/7 ×(x - 7/2) = 18`
`3/2 × x - 2/7 × x + 1 = 18`
`x × (3/2 - 2/7) = 18 - 1 = 17`
`x × 17/14 = 17`
`⇒ x = 17 : 17/14 = 14`
`i)`
`3600 : [(5 × x + 335) : x] = 50`
`(5 × x + 335) : x = 3600 : 50 = 72`
`5 × x + 335 = 72 × x`
`335 = 72 × x - 5 × x = 67 × x`
`x = 335 : 67 = 5`
`j)`
`(0,1 + x) + (0,2 + x) + ........... + (1,9 + x) = 76`
`(0,1 + 0,2 + .............. + 1,9) + (x + x + ...... + x) = 76`
`Đặt A = 0,1 + 0,2 + .............. + 1,9`
` A = 1,9 + 1,8 + .............. + 0,1`
` 2A = 2 + 2 + ................ + 2 ( có 19 số 2)`
` 2A = 2 × 19 = 38`
` A = 38 : 2 = 19`
`⇒ 19 + 19x = 76`
`19x = 57`
`x = 3`
