Wht do I put?? Can some one help pls

When keisha installed a fence along the 200 foot perimeter of her rectangular back yard, she left an opening for a gate.in the diagram below, she used x to represent the length in feet of the gate? what is the value? a. 10 b. 20 c. 25 d. 30

Emily is entering a bicycle race for charity. her mother pledges $0.90 for every 0.75 mile she bikes. if emily bikes 18 miles, how much will her mother donate?

What is the value of x in the equation7x+2y=48 when y=3