To solve this question we need to set up an equation.
Let's name the number of incorrect answers x.
We can set up an equation that's essentially:
(Points for correct answer)*(number of correct answers)+(points for incorrect answer)*(number of incorrect answers)=final score
When we plug in our numbers and variables it looks like this:
Subtract 15 from both sides
Divide both sides by -2
This means Smitha attempted 15 wrong answers, and that there were 18 questions in total.