-5=x/3minus 8 whats the answer

Just tell me how to set up the equation.

The perimeter of a rectangular lot of land is 436 ft. this includes an easement of x feet of uniform width inside the lot on which no building can be done. if the buildable area is 122 ft by 60 ft, determine the width of the easement. select one: a. 9 feet b. 18 feet c. 4.5 feet d. 7 feet

Is experimental probibilty the same as the observed frequency in math? i need the answer asap!