Let's use a Venn diagram to solve this problem. We have a total of 40 students in the class. 4 students offer neither Mathematics nor Physics, so we can subtract them from the total to get 36 students who offer at least one of the two subjects.

We know that 32 students offer Mathematics and 24 offer Physics. If we add these two numbers, we get 56, which is greater than the total number of students who offer at least one of the two subjects (36). This means that some students must be counted twice because they offer both Mathematics and Physics.

To find out how many students offer both subjects, we can subtract the total number of students who offer at least one of the two subjects (36) from the sum of the number of students who offer Mathematics and the number of students who offer Physics (56):

56 - 36 = 20

So, there are 20 students who offer both Mathematics and Physics.