What is the solution to this system of equations?

Can someone me with this problem i don't understand i need

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

How many sides does a regular polygon have if each exterior angle measure is 45 degrees explain your answer, i really don't understand this.