Short answer: There are 10 students in each van and 26 students in each bus.
13x+13y=468
3x+13y=368
3x+13y+100=468
3x+13y+100=13x+13y
3x+100=13x
100=10x
100/10=x
10=x
130+13y=468
468-130=13y
338=13y
338/13=y
26=y
So, x=10 and y=26. There are 10 students in each van and 26 students in each bus.
Checking my work:
(13*10)+(13*26)=130+338=468
(3*10)+(13*26)=30+338=368