Question

Que número diminuído de seus 2/5 e dos seus 3/7 é igual a 12?

Answer 1

$x- \frac{2x}{5} - \frac{3x}{7} =12\\\\ \frac{35x-(7\cdot2x)-(5\cdot3x)}{35}=12\\\\ \frac{35x-14x-15x}{35}=12\\\\ \frac{6x}{35} =12\\\\6x=35\cdot12 \\\\6x=420\\\\x= \frac{420}{6}\\\\\boxed{\boxed{x=70}}$