$\text{$\dfrac{a}{5}$ + $\dfrac{b}{3}$ = $\dfrac{13}{15}$}$
$\text{=> $\dfrac{3a}{15}$ + $\dfrac{5b}{15}$ = $\dfrac{13}{15}$}$
$\text{=> $\dfrac{3a + 5b}{15}$ = $\dfrac{13}{15}$}$
$\text{=> 3a + 5b = 13}$
$\text{Ta có bảng sau : Hình}$
$\text{Vậy a = 1 ; b = 2.}$