Question

x sobre 5 mais x sobre 2 igual a 21

Answer 1

$\frac{x}{5}+\frac{x}{2}=21\\\frac{2\cdot x}{2\cdot 5}+\frac{5\cdot x}{5\cdot 2}=21\\\frac{2x}{10}+\frac{5x}{10}=21\\\frac{2x+5x}{10}=21\\2x+5x=21\cdot 10\\7x=210\\x=210\div 7\\\boxed{\bold{x=30}}$