If you can answer the carter and the students one thank you.

For the carter one;
the equation would be 15h + 12= 72

h represents the hours, and since it has an hourly fee you'd have to multiply the amount of hours by 15. to solve for h, you'd have to isolate h. just subtract 12 from each side, after you do that the equation should be 15h=60. since you're multiply h and need to isolate it, you'd have to divide by 15 on both sides, so you get h=4 :)

students one:

7s+16=373 is the equation for this. s represents the students on the bus. to get s, you'd isolate the variable once again

s= 51

so there would be 51 students in each bus.