Hello,
Let assume x the number of half-dollars3x is the number of quarters.
The coins total $13.75.
[tex] 0.50 *x+ 0.25 *3x=13.75\\
\Rightarrow\ \dfrac{x}{2}+ \dfrac{3x}{4}=13.75\\
\Rightarrow\ \dfrac{2x}{4}+ \dfrac{3x}{4}=13.75\\
\Rightarrow\ \dfrac{5x}{4}=13.75\\
\Rightarrow\ 5x=4*13.75\\
\Rightarrow\ 5x=55\\
\Rightarrow\ x=11\\
[/tex]
11 is the number of half-dollars
33 is the number of quarters.
