Answer: Yes the mixed 3 1/4 is a rational number.
Step-by-step explanation:
The answer is 9 cubic units
First you have to find the angle B (check attachment)

Then you can find the last angle inside the triangle, which I'll call C

Now you can find angle A

3o'clock - directly to the right of the origin; on the x axis - (5,0)
6o'clock - directly below the origin; on the y-axis - (0,-5)
9o'clock - directly to the left of the origin; on the x-axis, (-5,0)
12o'clock - directly above the origin; on the y-axis, - (5,0)