The area of a parallelogram is 105 square feet. What is the base?

The answer is one and 1/3 + one and 2/3.
To get this answer, we must first need to understand improper fractions are (i guess) an 'uglier' version of mixed numbers because improper fractions can be converted to mixed numbers and vice versa making them pretty much the same thing. 
So an improper fraction is when the numerator is bigger than denominator.
(we also need to understand that for example: 12/3 is the same as 12 divided by 3)
So, what divided by what gives 3? Well 3*3=9 so if 9 is divided by 3 it will equal 3. Therefore we have an improper fraction of 9/3.

The basics of addition in fraction is when the numerator is the same, just add the top. So for simplicity's sake we will make out sum where both improper fraction's denominator is 3. So... what plus what equals 9? 4+5. 4 and 5 are chosen because both numbers are bigger than 3.
so now we have:
4/3 + 5/3
Now just turn the improper fraction into a mixed number and we get the answer of: one and 1/3 + one and 2/3, which equals 3