15=3+x+X

Solution for 15=3+x+X equation:

Simplifying
15 = 3 + x + X

Reorder the terms:
15 = 3 + X + x

Solving
15 = 3 + X + x

Solving for variable 'X'.

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

Add '-1X' to each side of the equation.
15 + -1X = 3 + X + -1X + x

Combine like terms: X + -1X = 0
15 + -1X = 3 + 0 + x
15 + -1X = 3 + x

Add '-15' to each side of the equation.
15 + -15 + -1X = 3 + -15 + x

Combine like terms: 15 + -15 = 0
0 + -1X = 3 + -15 + x
-1X = 3 + -15 + x

Combine like terms: 3 + -15 = -12
-1X = -12 + x

Divide each side by '-1'.
X = 12 + -1x

Simplifying
X = 12 + -1x