Answer:
Explanation:
Let H and P represent the number of history and physics textbooks.
We are told that:
1) H + P = 236/week, and
2) H = 3P [A disgrace, but that's a different problem]
We can substitute the definition of H in the second equation into the first:
H + P = 236/week
3P + P = 236/week
4P = 236
P = 59
H = 3P, so H = 3*(59) or 177
59 Physics and 177 History books for a total of 236 books sold that week.