Question 246187
The perimeter is 2*length + 2*width or 

P = 2*L +2*W = 210

The Length is 15 less than 2 times the width or L = 2*W-15

Substituting 2*W-15 for L in the first equation above we have:

2*(2*W-15) + 2*W = 210
4*W - 30 + 2*W  = 210 
6*W = 240
W = ?
Solve for W and then substitute that value in L = 2*W -15 to get the value for L.