Abus makes a stop at 2: 30,letting off 15 people and letting on 9.the bus makes another stop ten minutes later to let off 4 more people. how does the number of people on the bus after the second stop compare to the number of people on the bus before 2: 30 stop?

Whatever the initial number of people in the bus was, we know that this number underwent the following transformations: after the first stop, we have

After the second stop, we have

So, globally, there are 10 people less at the end.

it is a. 4.2 because 7.6-3.4 gets the remaining length of 4.2. i might be wrong but i am pretty sure this is the answer.