Hello :3
I'm not sure if this is exactly what you're looking for but it would be
a to the power of 7
and y to the power of 7
Hope This Helps!
Cupkake~
[tex](ay)^{7}[/tex]
recalling the law of exponents
[tex](ab)^{n}[/tex] = [tex]a^{n}[/tex] × [tex]b^{n}[/tex]