Step-by-step explanation:
[tex]\left\{\begin{array}{ccc}1x-1y=100&\text{multiply both sides by (-3)}\\\dfrac{3}{8}x+\dfrac{7}{8}y=2000&\text{multiply both sides by 8}\end{array}\right\\\\\left\{\begin{array}{ccc}-3x+3y=-300\\3x+7y=1600\end{array}\right\\\\\text{or}\\\\\left\{\begin{array}{ccc}1x-1y=100&\text{multiply both sides by 7}\\\dfrac{3}{8}x+\dfrac{7}{8}y=2000&\text{multiply both sides by 8}\end{array}\right\\\\\left\{\begin{array}{ccc}7x-7y=700\\3x+7y=1600\end{array}\right[/tex]
