1.THE PERIMETER OF A RECTANGLE IS TO BE NO GREATER THAN 300IN.,AN THE LENGTH MUST BE 125IN.FIND THE MAXIUM WIDTH OF THE RECTANGLE.

2. 3X-2Y=6

1. Perimeter = 2L + 2W <or= 300

L = 125
Therefore
250 + 2W <or= 300
2W <or= 50
W <or= 25 in
25 inches is the maximum width, W

2. That is a single equation with two unknowns. It can be rerarranged but not "solved" for both X and Y.
For example, 2Y = 3X -6
Y = (3/2) X -3

What are you being asked to do with that equation?