cứu huhuhuu Bài tập mẫu 18: Tìm x, biết:,$a.~x+\frac19=\frac{-7}{16}+\frac19$ $C.~x+\frac1{13}=\frac{-4}9+\frac1{13}$,$b.~x+\frac14=\frac25-(-\frac14)$ $d.~x+\frac59=\frac{-7}{13}-(-\frac59)$,Bài tập mẫu 19. Tìm x , biết:,$a.~x+\frac9{11}=\frac{-2}5+\frac9{11}$ $b.~x+\frac17=\frac34-(-\frac17)$,$C.~x+\frac{13}{27}=\frac{-4}9-\frac{14}{27}$ $d.~x+\frac38=\frac{-2}{19}-(-\frac38)$,Bài tập mẫu 20: Tìm x biết: $a.~\frac12x-\frac35=-\frac15$ $b.~\frac59x-\frac13x=\frac18+\frac{11}9x$

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18:

$$a)x+\frac{1}{9}=-\frac{7}{16}+\frac{1}{9}$$

$$x=-\frac{7}{16}+\frac{1}{9}-\frac{1}{9}$$

$$x=-\frac{7}{16}$$

$$b)x+\frac{1}{4}=\frac{2}{5}-\left(-\frac{1}{4}\right)$$

$$x+\frac{1}{4}=\frac{2}{5}+\frac{1}{4}$$

$$x=\frac{2}{5}+\frac{1}{4}-\frac{1}{4}$$

$$x=\frac{2}{5}$$

$$c)x+\frac{1}{13}=-\frac{4}{9}+\frac{1}{13}$$

$$x=-\frac{4}{9}+\frac{1}{13}-\frac{1}{13}$$

$$x=-\frac{4}{9}$$

$$d)x+\frac{5}{9}=-\frac{7}{13}-\left(-\frac{5}{9}\right)$$

$$x+\frac{5}{9}=-\frac{7}{13}+\frac{5}{9}$$

$$x=-\frac{7}{13}+\frac{5}{9}-\frac{5}{9}$$

$$x=-\frac{7}{13}$$

19:

$$a)x+\frac{9}{11}=-\frac{2}{5}+\frac{9}{11}$$

$$x=-\frac{2}{5}+\frac{9}{11}-\frac{9}{11}$$

$$x=-\frac{2}{5}$$

$$b)x+\frac{1}{7}=\frac{3}{4}-\left(-\frac{1}{7}\right)$$

$$x+\frac{1}{7}=\frac{3}{4}+\frac{1}{7}$$

$$x=\frac{3}{4}+\frac{1}{7}-\frac{1}{7}$$

$$x=\frac{3}{4}$$

$$c)x+\frac{13}{27}=-\frac{4}{9}-\frac{14}{27}$$

$$x=-\frac{4}{9}-\frac{14}{27}-\frac{13}{27}$$

$$x=\frac{4}{9}-\frac{27}{27}$$

$$x=-\frac{5}{9}$$

$$d)x+\frac{3}{8}=-\frac{2}{19}-\left(-\frac{3}{8}\right)$$

$$x+\frac{3}{8}=-\frac{2}{19}+\frac{3}{8}$$

$$x=-\frac{2}{19}+\frac{3}{8}-\frac{3}{8}$$

$$x=-\frac{2}{19}$$

20:

$$a)\frac{1}{2}x-\frac{3}{5}=-\frac{1}{5}$$

$$\frac{1}{2}x=-\frac{1}{5}+\frac{3}{5}$$

$$\frac{1}{2}x=\frac{2}{5}$$

$$x=\frac{4}{5}$$

$$b)\frac{5}{9}x-\frac{1}{3}x=\frac{1}{8}+\frac{11}{9}x$$

$$\frac{5}{9}x-\frac{1}{3}x-\frac{11}{9}x=\frac{1}{8}$$

$$-x=\frac{1}{8}$$

$$x=-\frac{1}{8}$$.