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

The answer will be the three sides have the same length, the sum of the lengths of two sides is equal to the length of the third side. Hope it help!