Question

In a class test$\left(+3\right)$ marks are given for every correct answer and$\left(-2\right)$ marks are given for every incorrect answer and no marks for not attempting any question.

Mohini scored$-5$ marks. If she has got $7$ the correct answer. How many questions has she attempted incorrectly?

Answer 1

Marks for every correct answer$=+3$

and Marks for every correct answer$=-2$

Mohini scored$=$ the number of the correct questions$\times \left(+3\right)+$ number of the incorrect answer$\times \left(-2\right)$

Number of the correct questions of Mohini $=7$(given)

Let the number of incorrect answer of Mohini is $\mathrm{a}$

$$\begin{gathered} -5=7\times \left(+3\right)+\mathrm{a}\times \left(-2\right) \\ -5=21+\mathrm{a}\times \left(-2\right) \\ -2\mathrm{a}=-5-21 \\ -2\mathrm{a}=-26 \\ \mathrm{a}=\frac{-26}{-2} \\ \mathrm{a}=13 \end{gathered}$$

$\therefore$Mohini attempted $13$ questions incorrectly