Answer: 38
Step-by-step explanation: In order to find the area you need to figure out all your sides. Now thankfully it's just a rectangle or this would be a bit more complicated haha!
The first step is to understand what all the sides are. Since you know you have a perimeter of 78 and base of 38, all you need to do is add 38 +38. The reason is that that's on both long sides of a rectangle. This now leaves you with a number of 76.
Second step: Take the number 76 and subtract it your perimeter 78. This obviously leaves you with the number 2, which you'll have 1 on the shorter sides.
Therefore Area: 38 x 1 = 38
Hope it helps