First, add up all of the numbers.
6+4+7+3=20
3 out of the 20 students favour Science.
You need to find the total out of 400, so set up a proportion.
3/20 = x/400
To solve the proportion, you multiply 3 and 400 to get 1,200, then divide it by 20, which is 60.
So out of the 400 student, 60 favour Science.
