algebra
posted by
lovey
.
Solve the linear equation using any technique you have learned. Name the technique. Check.
3x + 12 = 7x  28
I know the answer is x = 4
and I know that substitution is the technique that is used, but I can't figure out how to set this up

algebra 
Marie
3(4) + 12 = 7(4)  28
12 + 12 = 28  28
0 = 0

algebra 
Reiny
3x + 12 = 7x  28
Add 7x to both sides
3x + 12 + 7x = 7x  28 + 7x
10x + 12 = 28
Now subtract 12 from both sides
10x + 12  12 = 28  12
10x = 40
now divide both terms by 10
x = 4