Answer: (4,-4)
Step-by-step explanation:
Reflection across the x axis means [tex](x,y) \longrightarrow (x,-y)[/tex], so [tex](3,7) \longrightarrow (3,-7)[/tex].
Reflection across the y axis means [tex](x,y) \longrightarrow (-x,y)[/tex], so [tex](3,-7) \longrightarrow (-3,-7)[/tex].
Then, [tex](-3,-7) \longrightarrow R'\boxed{(4,-4)}[/tex]