ANSWER:
$35
STEP-BY-STEP EXPLANATION:
To know the payment we must multiply the value of the shirt by the percentage remaining after applying the discount, just like this:
[tex]\begin{gathered} c=50\cdot(1\text{00\%-30\%)= 50}\cdot70\text{\%} \\ c=50\cdot\frac{70}{100}=35 \end{gathered}[/tex]