#### Answer

a=$\frac{75}{2}$

#### Work Step by Step

In order to solve for d the proportion $\frac{5}{8}$=$\frac{a}{60}$, we must apply the Cross Products Property of a Proportion that states that if $\frac{a}{b}$=$\frac{c}{d}$, where b$\ne$0 and d$\ne$0, then ad=bc.
We'll set a=5, b=8, c=a and d=60, and apply the Property.
$\frac{5}{8}$=$\frac{a}{60}$
(5)(60)=(a)(8)
300=8a
Then, to solve for a, we'll divide by 8 on both sides of the equation
$\frac{300}{8}$=$\frac{8a}{8}$
a=$\frac{300}{8}$=$\frac{75}{2}$