I really need help with these 3 problems, can any one show me how to do them?

1) Suppose the cell of a natural beehive is a regular hexagon with a side length of 5 mm. What is the width of each cell? (The width is the distance between parallel sides.)

2) The diagonal of a square is 12 inches. Find the area. Round to the nearest tenth.

3) A fan at a sporting event is sitting at point A in the bleachers. The bleacher seating has an angle of elevation of 30 degrees and a base length of 90 feet. Find the height of the bleachers and round to the nearest tenth.

Thank you for your help :)