Question 1206099
A textbook store sold a combined total of 215 psychology and history textbooks in a week. The number of psychology textbooks sold was 57 more than the number of history textbooks sold. How many textbooks of each type were sold?

Psycology books sold be x

History books sold be y

 store sold a combined total of 215 psychology and history textbooks in a week.

x+y=215.....................................(1)

 store sold a combined total of 215 psychology and history textbooks in a week.

x=y+57
x-y=57.........................................(2)

add 1 & 2

2x = 272

x= 272/2= 136

215-136=79

79 history textbooks and 136 psychology textbooks were sold.