When you multiply a same number but with different powers, you can simply add the powers together. So, in your question, add the powers -1 and -7 together.
7^(-1) x 7^(-7) = 7^(-8)
When you divide a same number but with different powers, you subtract the power at the top with the power from the denominator. So, -8 - (-7) = -1.
7^(-8) / 7^(-7) = 7^(-1)
So your answer would be 7^(-1).
Hopefully my explanation was clear?
Evaporation is a type of vaporization that occurs on the surface of a liquid as it changes into the gas phase. The surrounding gas must not be saturated with the evaporating substance. When the molecules of the liquid collide, they transfer energy to each other based on how they collide with each other. Wikipedia
