21=(4A)-(3A)+6A

Solution for 21=(4A)-(3A)+6A equation:

Simplifying
21 = (4A) + -1(3A) + 6A

Remove parenthesis around (3A)
21 = (4A) + -1 * 3A + 6A

Multiply -1 * 3
21 = (4A) + -3A + 6A

Combine like terms: (4A) + -3A = 1A
21 = 1A + 6A

Combine like terms: 1A + 6A = 7A
21 = 7A

Solving
21 = 7A

Solving for variable 'A'.

Move all terms containing A to the left, all other terms to the right.

Add '-7A' to each side of the equation.
21 + -7A = 7A + -7A

Combine like terms: 7A + -7A = 0
21 + -7A = 0

Add '-21' to each side of the equation.
21 + -21 + -7A = 0 + -21

Combine like terms: 21 + -21 = 0
0 + -7A = 0 + -21
-7A = 0 + -21

Combine like terms: 0 + -21 = -21
-7A = -21

Divide each side by '-7'.
A = 3

Simplifying
A = 3