# How do you solve the proportion 7:5 = x:20?

Apr 29, 2015

$7 : 5 \equiv \left(7 \times 4\right) : \left(5 \times 4\right) \equiv 28 : 20$

that
$7 : 5 = x : 20$
$\rightarrow x = 28$

Alternately we could rewrite the ratios as fractions:
$\frac{7}{5} = \frac{x}{20}$

Multiplying both sides by $20$
$x = \frac{7 \times 20}{5} = 7 \times 4 = 28$