Let v = the number of students in a van and b = the number in a bus.
7v + 12b = 554
14v +4b = 348
Subtract 3 times equation 2 from equation 1
7v + 12b = 554
-42v -12b = -1044
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-35v + 0 = -490
v = 490/35 = 14
Substitute 14 for v in the first equation
7(14)+12b = 554
12b = 554 - 98 = 456
b = 456/12 = 38
There were 14 students in each van and 38 students in each bus.