21+4a-7(a-1)=a

Solution for 21+4a-7(a-1)=a equation:

Simplifying
21 + 4a + -7(a + -1) = a

Reorder the terms:
21 + 4a + -7(-1 + a) = a
21 + 4a + (-1 * -7 + a * -7) = a
21 + 4a + (7 + -7a) = a

Reorder the terms:
21 + 7 + 4a + -7a = a

Combine like terms: 21 + 7 = 28
28 + 4a + -7a = a

Combine like terms: 4a + -7a = -3a
28 + -3a = a

Solving
28 + -3a = a

Solving for variable 'a'.

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

Add '-1a' to each side of the equation.
28 + -3a + -1a = a + -1a

Combine like terms: -3a + -1a = -4a
28 + -4a = a + -1a

Combine like terms: a + -1a = 0
28 + -4a = 0

Add '-28' to each side of the equation.
28 + -28 + -4a = 0 + -28

Combine like terms: 28 + -28 = 0
0 + -4a = 0 + -28
-4a = 0 + -28

Combine like terms: 0 + -28 = -28
-4a = -28

Divide each side by '-4'.
a = 7

Simplifying
a = 7