Solving with substitution:
1. Express [tex]x[/tex] from first equation:
[tex]9x+8y=-3[/tex]
[tex]9x=-3-8y[/tex]
[tex]x=\frac{-3-8y}{9}=-\frac{3+8y}{9}[/tex]
2. Replace [tex]x[/tex] in second equation with found value and solve it:
[tex]5(-\frac{3+8y}{9})-2y=-21[/tex]
[tex]-\frac{15+40y}{9}-2y=-21[/tex]
[tex]-\frac{15+40y}{9}-\frac{18y}{9}=-21[/tex]
[tex]\frac{15+40y}{9}+\frac{18y}{9}=21[/tex]
[tex]\frac{15+40y+18y}{9}=21[/tex]
[tex]\frac{15+58y}{9}=21[/tex]
[tex]15+58y=21*9[/tex]
[tex]58y=189-15[/tex]
[tex]58y=174[/tex]
[tex]y=\frac{174}{58}=3[/tex]
3. Replace [tex]y[/tex] in first equation with found value and solve it:
[tex]9x+8*3=-3[/tex]
[tex]9x+24=-3[/tex]
[tex]9x=-3-24[/tex]
[tex]9x=-27[/tex]
[tex]x=\frac{-27}{3}=-9[/tex]
So, [tex]x=-9[/tex] and [tex]y=3[/tex]
