3c+2(21-2c)=34

Solution for 3c+2(21-2c)=34 equation:

Simplifying
3c + 2(21 + -2c) = 34
3c + (21 * 2 + -2c * 2) = 34
3c + (42 + -4c) = 34

Reorder the terms:
42 + 3c + -4c = 34

Combine like terms: 3c + -4c = -1c
42 + -1c = 34

Solving
42 + -1c = 34

Solving for variable 'c'.

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

Add '-42' to each side of the equation.
42 + -42 + -1c = 34 + -42

Combine like terms: 42 + -42 = 0
0 + -1c = 34 + -42
-1c = 34 + -42

Combine like terms: 34 + -42 = -8
-1c = -8

Divide each side by '-1'.
c = 8

Simplifying
c = 8