Help with Area and Volume

If x is 6, then 7x= a. 13 b. 42 c. 42x d. 76

Someone me! if you’re smart you can solve this!

Afarmer has a large field that is x feet in length. he wants to fence in a rectangular section in the middle of the field , leaving a length of 100 feet of open field behind each end of the fenced rectangle.he also wants the width of the fenced-in space to be 100 feet less than its length. find the expressions to represent the length and width of the fenced section of the field