Erika calculated that she would spend $115 on school supplies this year. she actually spent $82.50 on school supplies. what is erika’s percent of error

Percent of error is the same as percent of change so

115 -82.5=33 
so you have to take the original number and divid it by 33 so
33/115 which is .2869565217 i think you have to round it so it is .29 then you have to turn it into a percent which you move the decimal twice to the right to get 29%