am i the only one who horrible at remembering equations? like the only on i remember are to find the area/perimeter of a square/rectangle

Answer asap a family of two adults and three children went to a water park. admission to the water park costs $18 per person. nora used the expression 12(18)+3(18) to model the total cost for the family, and alex used the expression 5(18) which property of operations makes both of their expressions correct?