Question

даю 21 балл.      а3\5-13\45 б1\3-8\27 в1\2-1\3 г3\5-1\3
и ещё выполните вычитание и проверте сложением а5\12-1\3 б1\5-3\20 в7\8-5\12 г9\10-1\6
ну и ещёнайдите число икс для которого верно равенство 1\3+икс=5\12

Answer 1

№1.
$\frac{3}{5} - \frac{13}{45} = \frac{3*9 - 13}{45} = \frac{27-13}{45}= \frac{14}{45} \\ \\ \frac{1}{3} - \frac{8}{27} = \frac{1*9 - 8 }{27} = \frac{1}{27} \\ \\ \frac{1}{2} - \frac{1}{3} = \frac{1*3 - 1*2}{6} = \frac{1}{6} \\ \\ \frac{3}{5} - \frac{1}{3} = \frac{3*3 - 1*5}{15} = \frac{9-5}{15}= \frac{4}{15}$

№2.
$\frac{5}{12} - \frac{1}{3} = \frac{5 - 1*4}{12} = \frac{5-4}{12} = \frac{1}{12} \\ \\ \frac{1}{12} + \frac{1}{3} = \frac{1+1*4}{12} = \frac{1+4}{12} = \frac{5}{12} \\ \\ \\ \frac{1}{5} - \frac{3}{20} = \frac{1*4-3}{20} = \frac{1}{20} \\ \\ \frac{1}{20} + \frac{3}{20} = \frac{4}{20} = \frac{4:4}{20:4} = \frac{1}{5}$
$\frac{7}{8} - \frac{5}{12} = \frac{7*3}{8*3} - \frac{5*2}{12*2} = \frac{21-10}{24} = \frac{11}{24} \\ \\ \frac{11}{24} + \frac{5}{12} = \frac{11+5*2}{24} = \frac{21}{24} = \frac{21:3}{24:3} = \frac{7}{8} \\ \\ \\ \frac{9}{10} - \frac{1}{6} = \frac{9*3-1*5}{30} = \frac{27-5}{30} = \frac{22}{30} = \frac{22:2}{30:2} = \frac{11}{15} \\ \\ \frac{11}{15} + \frac{1}{6} = \frac{11*2+1*5}{30} = \frac{22+5}{30} = \frac{27:3}{30:3} = \frac{9}{10}$
№3.
$\frac{1}{3} +x= \frac{5}{12} \\ \\ x= \frac{5}{12} - \frac{1}{3} = \frac{5-1*4}{12} = \frac{5-4}{12}\\ \\ x= \frac{1}{12}$
проверим:
$\frac{1}{3} + \frac{1}{12}= \frac{1*4+1}{12} = \frac{5}{12}$