tìm x, biết

Câu 19. a) $~x+\frac14=\frac34$ Ta có: $~x = \frac34 - \frac14$ $~x = \frac{3-1}{4}$ $~x = \frac{2}{4}$ $~x = \frac{1}{2}$ b) $~\frac34-\frac25x=\frac{29}{60}$ Ta có: $~\frac25x = \frac34 - \frac{29}{60}$ $~\frac25x = \frac{45}{60} - \frac{29}{60}$ $~\frac25x = \frac{16}{60}$ $~\frac25x = \frac{4}{15}$ Nhân cả 2 vế với $\frac{5}{2}$: $~x = \frac{4}{15} \times \frac{5}{2}$ $~x = \frac{4 \times 5}{15 \times 2}$ $~x = \frac{20}{30}$ $~x = \frac{2}{3}$ c) $~2x-\frac13=\frac{-5}6$ Ta có: $~2x = \frac{-5}{6} + \frac13$ $~2x = \frac{-5}{6} + \frac{2}{6}$ $~2x = \frac{-3}{6}$ $~2x = \frac{-1}{2}$ Chia cả 2 vế cho 2: $~x = \frac{-1}{2} \div 2$ $~x = \frac{-1}{2} \times \frac{1}{2}$ $~x = \frac{-1}{4}$ d) $~2-x:\frac34=\frac12$ Ta có: $~x:\frac34 = 2 - \frac12$ $~x:\frac34 = \frac{4}{2} - \frac12$ $~x:\frac34 = \frac{3}{2}$ Nhân cả 2 vế với $\frac{3}{4}$: $~x = \frac{3}{2} \times \frac{3}{4}$ $~x = \frac{9}{8}$ Đáp số: a) $~x = \frac{1}{2}$ b) $~x = \frac{2}{3}$ c) $~x = \frac{-1}{4}$ d) $~x = \frac{9}{8}$