Question

A textbook store sold a combined total of 207 psychology and biology textbooks in a week. The number of biology textbooks sold was 59 less than the number of psychology textbooks sold. How many textbooks of each type were sold?

Answer 1

p+ b= 207
p-59= b

P+ (P-59)=207
2p-59=207:

2p =207+59
p=266/2
P=133
b=133-59
b=74
psych books= 133
biology books= 74
74+133= 207(Check)