Đáp án:
`a)` `\frac{2}{3}`
`b)` `\frac{-189}{4}`
Giải thích các bước giải:
`a)` `\frac{1}{3} + \frac{2}{5} ( x + 1 ) = 1`
`=> \frac{2}{5} ( x + 1 ) = 1 - \frac{1}{3}`
`=> \frac{2}{5}( x + 1 ) = \frac{2}{3}`
`=> x + 1 = \frac{2}{3} : \frac{2}{5}`
`=> x + 1 = \frac{5}{3}`
`=> x = \frac{5}{3} - 1 `
`=> x = \frac{2}{3}`
Vậy `x = \frac{2}{3}`.
`b)` `\frac{1}{4} + \frac{1}{3} : 3x = -5 `
`=> \frac{1}{4} + \frac{1}{9}x = -5`
`=> \frac{1}{9}x = - 5 - \frac{1}{4}`
`=> \frac{1}{9}x = \frac{-21}{4}`
`=> x = \frac{-21}{4} : \frac{1}{9}`
`=> x = \frac{-189}{4}`
Vậy `x = \frac{-189}{4}` .
