123=6k+3(5+7k)

Solution for 123=6k+3(5+7k) equation:

Simplifying
123 = 6k + 3(5 + 7k)
123 = 6k + (5 * 3 + 7k * 3)
123 = 6k + (15 + 21k)

Reorder the terms:
123 = 15 + 6k + 21k

Combine like terms: 6k + 21k = 27k
123 = 15 + 27k

Solving
123 = 15 + 27k

Solving for variable 'k'.

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

Add '-27k' to each side of the equation.
123 + -27k = 15 + 27k + -27k

Combine like terms: 27k + -27k = 0
123 + -27k = 15 + 0
123 + -27k = 15

Add '-123' to each side of the equation.
123 + -123 + -27k = 15 + -123

Combine like terms: 123 + -123 = 0
0 + -27k = 15 + -123
-27k = 15 + -123

Combine like terms: 15 + -123 = -108
-27k = -108

Divide each side by '-27'.
k = 4

Simplifying
k = 4