Answer:
A=-2 and B=3
Step-by-step explanation:
Step 1) Solve the first equation for A:
a+3b=7
a+3b-3b=7-3b
a+0=7-3b
a=7-3b
Step 2) Substitute (7-3b) for a in the second equation and solve for b:
2a=b-7 becomes:
2(7-3b)=b-7
(2*7)-(2*3b)=b-7
14-6b=b-7
14+7-6b+6b=b+6b-7+7
21-0=1b+6b-0
21=(1+6)b
21=7b
7b/7=21/7
=3
a=7-3b becomes:
a=7-(3*3)
a=7-9
a=-2
