Answer: a = 2
Subtract 9a from both sides.
9a and -9a then cancel out and 7a - 9a = -2a
Divide both sides by -2
-2 and -2 cancels out
-4/-2 = 2 leaving you with a = 2
To check your answer plug it in to wherever it says a.
9(2) - 4 = 7(2)
18 - 4 = 14
14 = 14 which is true.