Why Multiply When You're about to Divide?

The best way of approaching the restriction map is to first draw a circle. Next draw on the cutting points for one of the restriction enzymes. Consider the second restriction enzyme and see if you can place the cutting sites such that they are the correct size for both enzymes together, but also satisfy the second enzyme on its own. There may be several possibilities at these points. Use the data for the third restriction enzyme to eliminate all the possibilities bar one.

Note that some restriction maps are not unique, in that the data given may allow more than one valid map to be drawn.