Question

Solve by substitution -3x-2y=5.5 x+3y=7.5

Answer 1

$\bf \begin{cases} -3x-2y=5.5\\[-0.5em] \hrulefill\\ x+3y=7.5\\ \boxed{x}=7.5-3y \end{cases}~\hspace{5em}\stackrel{\textit{substituting \underline{x} in the 1st equation}}{-3\left( \boxed{7.5-3y} \right)-2y=5.5} \\\\\\ -22.5+9y-2y=5.5\implies -22.5+7y=5.5\implies 7y=28 \\\\\\ y=\cfrac{28}{7}\implies y=4 \\\\\\ \stackrel{\textit{substituting the found \underline{y} in the 2nd equation}}{x+3(4)=7.5\implies x+12=7.5}\implies x=-4.5 \\\\[-0.35em] \rule{34em}{0.25pt}\\\\ ~\hfill (-4.5,4)~\hfill$