What did does it mean to draw a cell “to scale”?

What it means when they say draw "to scale" the size you draw has to be relative or similar to its actual size.

For example if you draw a 100-foot building with windows 5 ft high building and scale it down where 1 inch = 10 ft. The drawing of the building would be 10 inches tall with windows 0.5 in high.  

Since you are drawing a cell, it would be a bit different. When you select a size of the cell you will draw, the organelles should be sized or scaled to the size it would be if the cell were actually that big.

In other words, it should be proportion to the actual size of the cell.

If you look at the head face of a penny for example, you would see President Licoln's head scaled down to the size of a penny. The eyes and nose are proportioned to the size of the penny as well.

before it leaves the nucleus of a eukaryotic cell, mrna is altered in the following ways: - a cap is added to the 5' end of the mrna molecule; - a poly a tail is added to the 3' end; - introns are removed and exons are spliced together.