The formula for area is length x width
So there is a rectangle with a length of 5 and a width of 9. To find the area you must multiply 5 and 9, which is 45. That's your area.
Now say you have a triangle. That triangle has a length of 46 and a height of 99. Again, l x w. 46 x 99 =4554.
Any other questions, let me know.