How do you get the answer for 820 decreased by 25%

What is the value of the expression below? (81^2)^1/8

The length of a rectangle is x times the square root of 100. the width is one-half y more than three-halves x. given that the area of the rectangle is 125 cm2, which equation could represent the rectangle in terms of x and y? a) 5xy − 15x = 125 b) 5xy + 15x = 125 c) 15x2 − 5xy = 125 d) 15x2 + 5xy = 125

Labc is reflected across x = 1 and y = -3. what are the coordinates of the reflection image of a after both reflections?