They marked up the bicycle price by $150 - $120 = $30
So, we want to know what percentage of $120 equals $30.
We have the following equivalence:
$30 → ?
$120 → 100%
If we divide both sides we have equal results:
[tex]\begin{gathered} \frac{30}{120}=\frac{\text{?}}{100} \\ \frac{3}{12}=\frac{?}{100} \\ \frac{1}{4}=\frac{?}{100} \end{gathered}[/tex]We multiply by 100 both sides in order to find the unknown value
[tex]\begin{gathered} \frac{1}{4}\cdot100=\frac{?}{100}\cdot100 \\ 25=\text{?} \end{gathered}[/tex]