Question

A textbook store sold a combined total of 220 psychology and biology textbooks in a week. The number of biology textbooks sold was 64 less than the number of psychology textbooks sold. How many textbooks of each type were sold?

Answer 1

Explanation:

Answer 2

This problem can be solved by using a system of linear equations. Let's denote:

P = the number of psychology textbooks sold, and

B = the number of biology textbooks sold.

We know from the problem statement that:

1) P + B = 220 (the total number of textbooks sold is 220)

2) B = P - 64 (the number of biology textbooks sold is 64 less than the number of psychology textbooks)

We can substitute equation 2 into equation 1 to find the value of P:

P + (P - 64) = 220

2P - 64 = 220

2P = 220 + 64

2P = 284

P = 284 / 2

P = 142

So, 142 psychology textbooks were sold.

We can then substitute P = 142 into equation 2 to find B:

B = 142 - 64

B = 78

Therefore, 142 psychology textbooks and 78 biology textbooks were sold.