7) 1.75c+7.50. If you knew the amount of cupcakes you would multiply that number by 1.75, but you don't know it, so we represent it with c. If you only pay the 7.50 one time, then there's nothing to multiply it to.
8) $929.84. Multiply 36 gallons × $3.19 per gallon, and you get $114.84. Then, add the $815 for the Airbnb and you get $929.84
