20 балов тому кто решит этот пример

Решите задачу:

$\left \{ {{\frac{2u}{3}-\frac{5m}{4}=-3\; |\cdot 12} \atop {\frac{5u}{6}+\frac{7m}{8}=6\; |\cdot 24}} \right. \; \left \{ {{8u-15m=-36} \atop {20u+21m=144}} \right. \; \left \{ {{u=\frac{15m-36}{8}} \atop {20\cdot \frac{15m-36}{8}+21m=144}} \right.\\\\\\\left \{ {{u=\frac{15m-36}{8}} \atop {37,5m-90+21m=144}} \right.\; \left \{ {{u=\frac{15m-36}{8}} \atop {58,5m=234}} \right. \; \left \{ {{u=3} \atop {m=4}} \right.\\\\\\Otvet:\; \; u=3\; ,\; m=4\; .$