multiply: (3x-5)(-x+4) applying the distributive property, the expression becomes (3x)(-x)+(3x)(4)+(-5)(-x)+(-5)(4). What is the simpified product in standard form

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