21=3(2-3z)

Solution for 21=3(2-3z) equation:

Simplifying
21 = 3(2 + -3z)
21 = (2 * 3 + -3z * 3)
21 = (6 + -9z)

Solving
21 = 6 + -9z

Solving for variable 'z'.

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

Add '9z' to each side of the equation.
21 + 9z = 6 + -9z + 9z

Combine like terms: -9z + 9z = 0
21 + 9z = 6 + 0
21 + 9z = 6

Add '-21' to each side of the equation.
21 + -21 + 9z = 6 + -21

Combine like terms: 21 + -21 = 0
0 + 9z = 6 + -21
9z = 6 + -21

Combine like terms: 6 + -21 = -15
9z = -15

Divide each side by '9'.
z = -1.666666667

Simplifying
z = -1.666666667