Question

What is 12a equal to if 4a plus 6b = 10 and 2a-4b=12?

Answer 1

Equation 1: 4a + 6b = 10

*Subtract 6b on the right side of the equation
4a = 10 - 6b

*Divide 4 on the right side of the equation, leaving the variable all by itself
a = 10 - 6b / 4
a = (5 - 3b) / 2

Equation 2: 2a - 4b = 12

*Substitute (5 - 3b) / 2 for 'a' in the second equation
2(5 - 3b) / 2)) - 4b = 12

*Combine like terms
5 - 3b - 4b = 12
5 - (-7b) = 12

*Subtract 5 to both sides
5 - 5 - (-7b) = 12 - 5
-7b = 7

*Divide -7 to both sides
-7b / -7 = 7 / -7
b = -1

*Substitute -1 for 'b' 
2a - 4(-1) = 12
2a + 4 = 12

*Subtract 4 to both sides
2a + 4 - 4 = 12 - 4
2a = 8

*Divide 2 to both sides
2a / 2 = 8 / 2
a = 4

12a = ?

*Substitute 4 for 'a'
12(4) = 48

12a = 48

Answer 2

12a=x
4a+6b=10
2a+3b=5
2a-4b=12
a-2b=6
2a+3b+1=a-2b
a+5b+1=0
a=-1-5b

2(-1-5b)+3b=5
-2-10b+3b=5
-2-7b=5
-7b=7
7b=-7
b=-1

-1-5*-1=a
-1+5=a
4=a

4*12=48
12a=48

Hope this helps :)