Question

me ajudem e urgente!!!!!

Answer 1

Sistema de equações do primeiro grau:

$\boxed{\boxed{ \left \{ {{\frac{x}{2}=\frac{y}{5}} \atop {x+y=21}} \to \left \{ {{5x=2y} \atop {x+y=21}} \right. \right. \to x = 21-y}}$

Resolução:

$\left[\begin{array}{ccc}5(21-y) = 2y\\\\105-5y = 2y\\\\2y+5y = 105\\\\7y = 105\\\\y = \frac{105}{7} = 15\end{array}\right \to \left[\begin{array}{ccc}x = 21-y\\\\x = 21-15\\\\x = 6\end{array}\right \to \boxed{\boxed{S=\{6,15\} }}$

Espero ter ajudado. =^.^=