First we define the variables:
m = multiple choice questions
s = short answer questions
Next we need to satisfy 2 conditions:
1) There are a total of 40 questions. We can represent this mathematically using the variables I defined:
2) The multiple-choice questions are worth 2 points and the short-answer are worth 4 points but they need to total 100 points. This can also be represented mathematically:
By satisfying the conditions provided we were able to create the 2 equations!