Question

What does 12A equal?

Answer 1

4a+6b=10 
4a=10-6b 
a=(10-6b)/4 
a=(5-3b)/2 

2a-4b=12 
2((5-3b)/2)-4b=12 
(5-3b)-4b=12 
5-7b=12 
-7b=7 
b=-1

2a-4b=12 
2a-4(-1)=12 
2a+4=12 
2a=8 
a=4 

a=4, b=-1 

12a=48

Answer 2

Well if the rest of the equation looks like this
{4a+6b=10, 2a-4b=12}

Solve for 'a' in equation 2

2a-4b=12
2a=12+4b
a=6+2b

Substitute (6+2b) for 'a' in equation 10

4a+6b=10
4(6+2b)+6b=10
24+8b+6b=10
24+14b=10
14b=-14
b=-1

Substitute (-1) for 'b' in equation 2

2a-4b=12
2a-4(-1)=12
2a+4=12
2a=8
a=4

{a=4, b=-1}

--> 12a=48