90=x+21(2x)

Solution for 90=x+21(2x) equation:

Simplifying
90 = x + 21(2x)

Remove parenthesis around (2x)
90 = x + 21 * 2x

Multiply 21 * 2
90 = x + 42x

Combine like terms: x + 42x = 43x
90 = 43x

Solving
90 = 43x

Solving for variable 'x'.

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

Add '-43x' to each side of the equation.
90 + -43x = 43x + -43x

Combine like terms: 43x + -43x = 0
90 + -43x = 0

Add '-90' to each side of the equation.
90 + -90 + -43x = 0 + -90

Combine like terms: 90 + -90 = 0
0 + -43x = 0 + -90
-43x = 0 + -90

Combine like terms: 0 + -90 = -90
-43x = -90

Divide each side by '-43'.
x = 2.093023256

Simplifying
x = 2.093023256