Question 131641
Check our knowledge of the shape :REctangle
the perimeter = 2 length * 2 width
 L-W= 7  equation one
2L+2W=50 equation two 
  either by elimination or sub .
 slove for L in the eqaution one
 L= 7+W sub this value in the equation two instead of L

2L+2W=50
2(7+w)+2W=50
14+2w+2w=50
collect the like terms and isolate the Variable"letter " in one side
4w=36
w = 9
 L=7+9= 16