Question

a+b=70
$\frac{a}{b}= \frac{3}{7}$
a,b=?

Answer 1

[tex]a+b=70 \\ \frac{a}{b}= \frac{3}{7}=>7a=3b;~a= \frac{3b}{7} \\ Inlocuim: \\ \frac{3b}{7}+^{7)}b=^{7)}70 \\ \frac{3b}{7}+ \frac{7b}{7}= \frac{490}{7} |*7 \\ 10b=490 \\ \boxed{b=49} \\ a=70-49 \\ \boxed{a=21}[/tex]