The perimeter of a rectangle is given by:
P = 2l + 2w
where p is the perimeter of the rectangle
l is the length of the rectangle and w is the width of the rectangle
From the question length is given as: 3x-10 and the width is given to be x-7
substituting into the formula
P = 2l + 2w
P = 2(3x-10) + 2(x-7)
let's open the parenthesis and then simplifies
P = 6x - 20 + 2x - 14
P = 6x + 2x - 20 -14
P= 8x -34
Therefore the perimeter of the rectangle is equal to (8x- 34)