In transformations, the original figure is called "Pre-Image" and the figure obtained after the transformation is called "Image".
In this case, you know that the Pre-Image is the following point given in the exercise:
[tex](-7,4)[/tex]By definition, the rule of a reflection over the line
[tex]y=x[/tex]is the following:
[tex](x,y)\rightarrow\mleft(y,x\mright)[/tex]Therefore, applying this rule to the point given in the exercise, you get that its Image is:
[tex]\mleft(-7,4\mright)\rightarrow(4,-7)[/tex]The answer is:
[tex](4,-7)[/tex]