4. Solve the following system of equations:
3 + 2x - y = 0,
-3 - 7y = 10x
by using substitution, and by elimination.
2x−y=−310x+7y=−3
substitutiony=2x+310x+7(2x+3)=−324x+21=−324x=−24x=−1,y=1−−eliminationsubtract 5x the first equation from the second12y=12y=1, x=−1
+123 
