problem: One ticket to a show costs $\$20$ at full price. Susan buys $4$ tickets using a coupon that gives her a $25\%$ discount. Pam buys $5$ tickets using a coupon that gives her a $30\%$ discount. How many more dollars does Pam pay than Susan?
solution: We need to calculate the total purchase price that Susan paid and that Pam paid.
  
  Susan bought $4$ tickets with $25\%$ discount: $$4 \times \$20 = \$80.$$With a $25$ percent discount, she paid $\$80 * .75 = \$60.$
  
  Pam bought $5$ tickets with a $30\%$ discount: $$5 \times \$20 = \$100$$With a $30$ percent discount, she paid $\$100 * .70 = \$70.$
  
  Thus Pam paid $\$70 - \$60 = \$\boxed{10}$ more than Susan.