Answer :
[tex]-2x-y=-9 \\
5x-2y=18 \\ \\
\hbox{solve the first equation for y:} \\
-2x-y=-9 \ \ \ |+2x \\
-y=-9+2x \ \ \ |\times (-1) \\
y=9-2x \\ \\
\hbox{substitute 9-2x for y in the second equation:} \\
5x-2(9-2x)=18 \\
5x-18+4x=18 \\
9x-18=18 \ \ \ |\div 9 \\
x-2=2 \ \ \ |+2 \\
x=4 \\ \\
y=9-2x=9-2 \times 4=9-8=1 \\ \\
\boxed{(x,y)=(4,1)}[/tex]
-2x-y = -9
5x-2y=18
-solve for y in terms of x
-y= 2x-9
y=-2x+9
substitute
5x-2 ( -2x+9)=18
5x+4x -18=18
9x-18=18
9x= 36
x=4
substitute for x
-2 (4) -y= -9
-8 -y = -9
-y = -1
y= 1
ANSWER x= 4
y=1
hope this helps
