The senior class at high school a rented and filled 12 vans and 3 buses with243 students. high school b rented and filled 4 vans and 4 buses with 204 students. each van and each bus carried the same number of students. find the number of students in each van in each bus.

12v + 3b = 243
4v + 4b = 204multiply by -3

12v + 3b = 243
-12v - 12b = - 612 (result of multiplying by -3)
add
-9b = - 369
b = -369/-9
b = 41 <=== each bus holds 41 students

4v + 4b = 204
4v + 4(41) = 204
4v + 164 = 204
4v = 204 - 164
4v = 40
v = 40/4
v = 10 <== each van holds 10 students