Test points

A test has 20 questions. The test awards 3 points if the answer is correct and takes away 1 point if the answer is incorrect. A student answered five questions incorrectly. How many points did the student earn?​

Correct answer:

x =  40

Step-by-step explanation:

$$\begin{gathered} n=20 \\ i=5 \\ c=n-i=20-5=15 \\ x=c\cdot 3-i\cdot 1=15\cdot 3-5\cdot 1=40 \end{gathered}$$

Try another example