Price after the 25% discount: $21.75
This means that $21.75 is 75% of the original price. If x is the original price, then:
[tex]\begin{gathered} 75\text{\% of }x=21.75 \\ \frac{75}{100}\cdot x=21.75 \\ x=\frac{100\cdot21.75}{75} \\ \Rightarrow x=\text{ \$}29 \end{gathered}[/tex]