Помогите решит ! а)7/5/12+4/3/8 б)3/11/20+2/19/30 в)9/5/6-2/3/4 г)3/3/10-1/7/15

А) 7/5/12= $\frac{7*12}{5}$
4/3/8= $\frac{4*8}{3}$
⇒ $\frac{7*12}{5}$ + $\frac{4*8}{3}$ = $\frac{3*84+5*32}{15} = \frac{412}{15}$

б) $\frac{20*3}{11}+ \frac{30*2}{19} = \frac{19*20*3+30*2*11}{11*19} = \frac{1800}{209}$

в) $\frac{9*6}{5}- \frac{2*4}{3}= \frac{9*6*3-2*4*5}{15}= \frac{122}{15}$

г) $\frac{3*10}{3}- \frac{1*15}{7} = \frac{210-45}{21}= \frac{165}{21}$