Question 245764
a=2b
a-3=3(b-3)
substitute
2b-3=3(b-3)
2b-3=3b-9
subtract 2b from both sides
-3=b-9
add nine to both sides
6=b
a=2b=12
check
a-3=(3(b-3)
12-3=3(3)
9=9

ok