If P=360, then 360yd / 4 sides = 90yds each side. Now that it is a rectangle, the Length should be more than the width, so if the length is 20yds more than the width, do 90 - 20 two times, Width= [ (90yds - 20yds)*2 ]
To sum things up, Length = 110; Width = 70. | 110*2 = 220, 70 * 2 = 140, 220+140 = 360.
The answer to your question is x=-2y+4
1.7 meters are 17 decimeters