Let x = T/F questions
Let y = Multiple Choice questions
x + y = 20
3x + 11y = 100

Solve by any method mentioned.
If done algebraically:
x + y = 20
3x + 11y = 100
3(x + y = 20)
3x + 11 y = 100
3x + 3y = 60
3x + 11y = 100
8y = 40
8y = 40
y = 5
There are 5 multiple choice questions.
x + 5 = 20
x = 15
There are 15 T/F questions. 