3(21-3a)=6-a

Solution for 3(21-3a)=6-a equation:

Simplifying
3(21 + -3a) = 6 + -1a
(21 * 3 + -3a * 3) = 6 + -1a
(63 + -9a) = 6 + -1a

Solving
63 + -9a = 6 + -1a

Solving for variable 'a'.

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

Add 'a' to each side of the equation.
63 + -9a + a = 6 + -1a + a

Combine like terms: -9a + a = -8a
63 + -8a = 6 + -1a + a

Combine like terms: -1a + a = 0
63 + -8a = 6 + 0
63 + -8a = 6

Add '-63' to each side of the equation.
63 + -63 + -8a = 6 + -63

Combine like terms: 63 + -63 = 0
0 + -8a = 6 + -63
-8a = 6 + -63

Combine like terms: 6 + -63 = -57
-8a = -57

Divide each side by '-8'.
a = 7.125

Simplifying
a = 7.125