How many textbooks of wach were sold

Question

A textbook store sold a combined total of 219 chemistry and biology textbooks in a week. The number of biology textbooks sold was 43 less tan the number of chemistry textbooks sold. How many textbooks of each type were sold

Answer 1

c + b = 219

 

b + 43 = c

 

Substitute:  b + 43 + b = 219,   2b = 176,   b = 88, c = 131