Question

A textbook store sold a combined total of 315 physics and chemistry textbooks in a week. The number of physics textbooks sold was two times the number of chemistry textbooks sold. How many textbooks of each type were sold?

Answer 1

Let x = the number of chemistry textbooks.

x + 2x = 315

3x = 315

x = 105

Answer 2

p + c = 315
p =2c

Replace p with the 2c in the first equation.

2c + c = 315

solve for "c"

then you can find p.

Answer 3

Y=105
X=210