4 | = | 8 |

| |

x | 20 |

Cross multiply:
4 * 20 = x * 8
Simplifying
4 * 20 = x * 8
Multiply 4 * 20
80 = x * 8
Reorder the terms for easier multiplication:
80 = 8x
Solving
80 = 8x
Solving for variable 'x'.
Move all terms containing x to the left, all other terms to the right.
Add '-8x' to each side of the equation.
80 + -8x = 8x + -8x
Combine like terms: 8x + -8x = 0
80 + -8x = 0
Add '-80' to each side of the equation.
80 + -80 + -8x = 0 + -80
Combine like terms: 80 + -80 = 0
0 + -8x = 0 + -80
-8x = 0 + -80
Combine like terms: 0 + -80 = -80
-8x = -80
Divide each side by '-8'.
x = 10
Simplifying
x = 10