SOLUTION: This is a last Subsitution question, but this one says solve by either ;addition or subtraction. The problem is: 12a-5b=18 15a-5b=30 Please and Thank You=)

Algebra ->  Expressions-with-variables -> SOLUTION: This is a last Subsitution question, but this one says solve by either ;addition or subtraction. The problem is: 12a-5b=18 15a-5b=30 Please and Thank You=)      Log On


   

Question 130090This question is from textbook algebra
: This is a last Subsitution question, but this one says solve by either ;addition or subtraction.
The problem is:
12a-5b=18
15a-5b=30
Please and Thank You=) This question is from textbook algebra

Found 2 solutions by checkley71, oscargut:
Answer by checkley71(8403) About Me  (Show Source):
You can put this solution on YOUR website!
12A-5B=18 NOW SUBTRACT THE SECOND EQUATION
-15A+5B=-30
---------------------------------
-3A=-12
A=-12/-3
A=4 ANSWER.
12*4-5B=18
48-5B=18
-5B=18-48
-5B=-30
B=-30/-5
B=6 ANSWER.
PROOF:
15*4-5*6=30
60-30=30
30=30

Answer by oscargut(2103) About Me  (Show Source):
You can put this solution on YOUR website!
12a-5b=18
15a-5b=30
then
12a-5b=18
-15a+5b=-30
adding
-3a=-12
then
a=4
then
12(4)-5b=18
then
30-5b=0
then
b=6
R: a=4 and b=6