To answer this, set up a system of equations. What we know is that
5x + 2y = 100 And... x+y=38
x represents the unknown number of 5 points questions y represents the unknown number of 2 point questions
In my opinion the easiest way to solve this is to use substitution (that is when you find out the value of one variable, either x or y, and substitute that value as the variable).