What does 12A equal?

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

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