A science test has 15 questions. 2 points are given for each correct answer,and 1point is taken off for every incorrect answer.how many questions are incorrect

Question

I don't know how to solve this. 30 points??                                                                                                                                               +2 pnts = C

 

                     - 1 pnt = IC 

 

=+-_/? I am confused 

Answer 1

Hi, Maile

 

Okay, if there are 15 questions, let's call:

X = number of correct answers

15 - X = number of incorrect answers

If Kelly got 21 points then:

 

2X - (15 - X) = 21

 

2X -15 + X = 21

3X = 36

X = 12

15 - X = 3

 

So, Kelly got 12 answers correct  and 3 answers incorrect