First, isolate the A terms on the left side of the equation and the constants on the right side of the equation while keeping the equation balanced:
10A + color(red)(2A) = 60 - 2A + color(red)(2A)
(10 + 2)A = 60 - 0
12A = 60
Now we can solve for A by dividing each side of the equation by color(red)(12) which will also keep the equation balanced:
(12A)/color(red)(12) = 60/color(red)(12)
(color(red)(cancel(color(black)(12)))A)/cancel(color(red)(12)) = 5
A = 5