3 4/5 is the answer also the three is the whole number
To find the measurement of an exterior angle, simply take the corresponding interior angle and subtract it from 180. Since the interior and exterior angle together add up to a straight line, their values should equal 180 degrees.
Consider the cross-sectional right triangle shown in the figure.
One of its sides is the height of the pyramid, with length H. The other side is half of the square base, so its length is 81 m. The hypotenuse of this triangle is the height of one of the faces.
By right triangle trigonometry,

,
thus,

.
Answer: C) 52 m
First we calculate 20% of the price:
20% of 30$ is 0.2*30$=6$.
Then we subtract 6$ (that is 20% of the price) from 30$, and get 24$.
Thus, the sale price is 24$