Sysytem of 2 equations

Question

An exam worth 172 points contains 30 questions. Some questions are worth 2 points,
and the others are worth 9 points. How many 2 point and 9 point questions are on the
test?

Answer 1

We know x questions are worth 2 points each and (30-x) questions are worth 9 points each.

 

2x + 9 (30-x) = 172

 

2x + 270 - 9x = 172

 

-7x + 270 = 172

 

-7x = -98

 

x = 14

30 - x = 16

There are 14 2-point questions and 16 9-point questions.

Check:  (14 * 2) + (16 * 9) = 28 + 144 = 172