Area of a rectangle is length times width. So any pair of positive numbers that multiply together and make 60 could be a possible length and width:
1 and 60
2 and 30
3 and 20
etc.
And these are just the integers that work. We could also have:
1/2 and 120
1/10 and 600 and
etc.
I suspect that you have left out part of the problem that would allow us to figure out a specific length and width. The missing part may be something like "The length is 11 more than the width" or "The perimeter is 64".