Question

Por método de igualación
15a-11b=87
-12a-5b=-27

Answer 1

$\left \{ {{15a-11b=87} \atop {-12a-5b=-27}} \right. \\ \\ \left \{ {{15a-11b=87} \atop {12a+5b=27}} \right. \\ \\ \left \{ {{a= \frac{87+11b}{15} } \atop {a= \frac{27-5b}{12} }} \right. \\ \\ \frac{87+11b}{15}= \frac{27-5b}{12} \\ \\ 12*(87+11b)=15*(27-5b) \\ 1044+132b=405-75b \\ 132b+75b=405-1044 \\ 207b=-639 \\ \\ b=-\frac{71}{23} \\ \\ a= \frac{87+11b}{15} =\frac{87+11*(-\frac{71}{23})}{15} = \frac{87-\frac{781}{23}}{15} = \frac{244}{69}$