How many squares of shingles will it take to cover a 28 by 60?

I will assume that you mean 28 x 60 feet which would be 1680 square feet. A square of asphalt shingles is normally 100 square feet of coverage. Therefore, it would require approximately 17 squares of asphalt shingles to cover the specified area.

An allowance of 5 to 10 percent should also be made for waste. Additional material will be required to cover ridges, valleys, and other areas special areas.

Lowes and Home Depot have a good selection of books of roofing.