To calculate the discount we can use a rule of 3 so:
[tex]\begin{gathered} 500\to100 \\ x\to30 \end{gathered}[/tex]so the equation:
[tex]\begin{gathered} x=\frac{500\cdot30}{100} \\ x=150 \end{gathered}[/tex]So the total cost will be:
[tex]T=500-150=350[/tex]