00:01
So we know we have plus five points for every correct answer.
00:04
Let's call correct answers x.
00:06
And then negative 2.
00:08
So we minus 2 for every incorrect answer.
00:11
Let's call incorrect answer is y.
00:13
So we know five times our correct answers minus two times our incorrect answers gives us our total score.
00:19
Let's call it t.
00:21
So here we're interested in finding the number of incorrect questions, which is represented by y.
00:28
So we should solve this equation for y.
00:31
We could do that by first subtracting 5x to the other side.
00:35
So we'll have t minus 5x.
00:38
And now to get y by itself, we divide both sides by negative 2.
00:41
So we'll have y equals the total minus five times the amount of correct questions over negative 2.
00:50
So we can use this formula to answer the question.
00:54
We have y equals.
00:55
And in the first case, we have a total score of 24 marks...