What is the area of this triangle?

Sadie computes the perimeter of a rectangle by adding the length, l, and width, w, and doubling this sum. eric computes the perimeter of a rectangle by doubling the length, l, doubling the width, w, and adding the doubled amounts. write an equation for sadie’s way of calculating the

In a rectangle klmn, km = 6x + 16 and ln = 49. find the value of x

Me because i don't understand how to do it.: )