3(u-9)-4u=-21

Solution for 3(u-9)-4u=-21 equation:

Simplifying
3(u + -9) + -4u = -21

Reorder the terms:
3(-9 + u) + -4u = -21
(-9 * 3 + u * 3) + -4u = -21
(-27 + 3u) + -4u = -21

Combine like terms: 3u + -4u = -1u
-27 + -1u = -21

Solving
-27 + -1u = -21

Solving for variable 'u'.

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

Add '27' to each side of the equation.
-27 + 27 + -1u = -21 + 27

Combine like terms: -27 + 27 = 0
0 + -1u = -21 + 27
-1u = -21 + 27

Combine like terms: -21 + 27 = 6
-1u = 6

Divide each side by '-1'.
u = -6

Simplifying
u = -6