A class of 195 students went on a field trip. They took 7 vehicles, some cars and some buses. What is the number of cars and the number of buses they took if each car holds 5 students and each bus hold 45 students?

Ahh, these questions remind me of my 8th grade days, man I used to die on these questions huehue

Anyways, so let's get to it
Basic algebra, the object which is not in a set quantity, which we have to find, is the "some cars" and the "some buses"

So let the number of cars be x
Let the number of buses be y

So, since there are 7 vehicles,
# x + y = 7 #
Makes sense right

Now, it says that every car can carry 5 students, and every bus can carry 45 students, so in another way, we could represent this by saying

5 x Number of Cars + 45 x Number of buses
thus,
5x + 45y
And since 195 students went on the field trip, this means that
5x +45y = 195

So now we have two equations,
x + y = 7
5x + 45y = 195

We can solve this with substitution
x + y = 7
x = 7 - y

Thus, x = 7-y
Put this in this
5(7-y) + 45y = 195
35 - 5y + 45y = 195
35 +40y = 195
40y = 195 - 35
40y = 160
y = 160/40
y= 4

Thus, the number of buses, y, is 4

Now since there are 7 vehicles, and 4 are buses, then the other 3 are cars

You can double check this

Hope this helped :D