Answer:
8 books
Step-by-step explanation:
5+3=8
The answer is 12 including both sides and angles.
When you cut a square piece of paper from one point to the opposite point it should make two triangles.
Thus each triangle has 3 sides and 3 angles so two triangles has 6 angles and 6 sides
So 12, sides and angles added together.
We will have to use the formula for the area of a trapezoid on this problem, which is (
and
are the bases of the trapezoid and
is the height):

All we need to do is substitute the information we are given into our formula:

Now, let's just simplify the equation:




The missing base has a length of 13 units.