A salesman sells a car for $11 000. If he receives a commission of 4.5% on 2 points the first $10 000 and 7.5% on the remainder, what is the total commission
he gets?

It is very important to look at all the information's that are given in the question. these information's will in getting to the desired result.
initial number = 24
final number = 30
amount of increase = 30 - 24
                                  = 6
then
percentage increase = (6/24) * 100
                                    = 100/4 percent
                                    = 25 percent
so the percentage of increase is 25%. i hope the procedure is clear enough for you to understand. you can use this method for solving similar type of problems in future without requiring any from outside.