#### Answer

$y=5$

#### Work Step by Step

We are trying to solve for the given variable so that the proportion is true.
To determine if a proportion is true, we have to find if the cross products are equal.
The cross products of $\frac{a}{b}=\frac{c}{d}$ are $a \cdot d$ and $b \cdot c$.
$30*y=15*10$
$30y=150$
$30y\div30=150\div30$
$y=5$