we have:
GT = IF
GS = IS
therefore we have the following system of equations:
[tex]\begin{gathered} -3x+5y=11 \\ 3x+y=13 \end{gathered}[/tex]
and solve for x and y
[tex]\begin{gathered} 3x+y=13 \\ 3x+y-3x=13-3x \\ y=13-3x \\ -3x+5(13-3x)=11 \\ -3x+65-15x=11 \\ -18x+65=11 \\ -18x+65-65=11-65 \\ -18x=-54 \\ \frac{-18x}{-18}=-\frac{54}{-18} \\ x=3 \end{gathered}[/tex]
and for y:
[tex]\begin{gathered} y=13-3x \\ y=13-3(3) \\ y=13-9 \\ y=4 \end{gathered}[/tex]
answer:
x = 3
y = 4
