For a trip , one high school rented and filled 6 vans and 3 buses with 123 students. another high school instead fits it's 156 students into 7 vans and 4 buses . with each bus and van wearing the same number of students , how many students can a bus carry? how many students can a van carry ?

6v + 3b = 123multiply by 4
7v + 4b = 156multiply by -3

24v + 12b = 492 (result of multiplying by 4)
-21v - 12b = - 468 (result of multiplying by -3)
add
3v = 24
v = 24/3
v = 8

7v + 4b = 156
7(8) + 4b = 156
56 + 4b = 156
4b = 156 - 56
4b = 100
b = 100/4
b = 25

so a bus (b) holds 25 students and a van (v) holds 8 students