Hi,
[tex]\frac{x^{a} }{x^{b} } =x^{a-b}[/tex]
a)
[tex]\frac{x^{7} }{x^{3} }= x^{7-3} = x^{4}[/tex]
b)
[tex]\frac{y^{5} }{y^{4} } = y^{5-4} = y^{1} = y[/tex]
;)
