Answer
The work is wrong because when the student multiplies the second equations he forgets to multiply the -3 with the 4 as well, therefore causing his entire equation to be false.
Work Step by Step
Our two equations are:
1. 5x+4y=2
2. 3x+3y=-3
The student correctly multiplies the first equation by 3 which gives us
15x+12y=-6
However he creates a mistake in the second equation. When multiplying by 4 he forgets to multiply the last -3 with 4.
If we correctly multiply, we should get
12x+12y=-12.
From there we can subtract 12y from both equations and get
3x=18.
Then divide by 3 and we get
x=6.
Next we plug this back into our original first equation for x to get our y values:
30+4y=2
Solve for y and we get y=-7. We can also check our answer by substituting our answer in the second equation and we end up getting the same value.
