The picture isn't very clear
57% of students studied, which decomposes into 52% who both studied and saw an increase in their exam grade 5% who both studied and did Not see an increase in their exam grade The percentages above are relative to the whole population of 100 students, to get the requested probability, recall that: One way to find out the probability of an event is to Take the ratio of the number of times the event happened, over the total number of times the event could have happened. Total number of times the event happened: 52 = 52% of 100 students studied and saw an increase in their exam grade Total number of times the event could have happened: 57 = 57% of 100 students studied
Given:
The system of equations:


To find:
The number that can be multiplied by the second equation to eliminate the x-variable when the equations are added together.
Solution:
We have,
...(i)
...(ii)
The coefficient of x in (i) and (ii) are 1 and
respectively.
To eliminate the variable x by adding the equations, we need the coefficients of x as the additive inverse of each other, i.e, a and -a So, a+(-a)=0.
It means, we have to convert
into -1. It is possible if we multiply the equation (ii) by -5.
On multiplying equation (ii) by -5, we get
...(iii)
On adding (i) and (iii), we get

Here, x is eliminated.
Therefore, the number -5 can be multiplied by the second equation to eliminate the x-variable.