An acute angle is infact 90 degrees, therefore your answer is correct.
(8x2.3)= (18.4)
(2.1x4)= (8.4)
Now you should have:
41-9+18.4-15+8.4
9+18= 27
15+8.4= 23.4
Should have:
41-27-23.4= -9.4
If there were 6 pieces and Keith ate 2 of the pieces, then there would be 4 pieces left.

and when you reduce it it would be
0.8p - 50 < = 150
0.8p < = 150 + 50
0.8p < = 200
p < = 200/0.8
p < = 250
the reason I set it up this way is because when it is 20% off, u r actually paying 80% of the original price (p)....80% of the original price is written as 0.8p...then u subtract ur 50 dollar discount coupon...- 50.....and if all she can spend is 150....it would be less then or equal to 150. So the most she can spend on the phone is 250
Volume of cube = 1/3 * pi * r^2 * h
83.74 = 1/3 x 3.14 x r^2 x 5 = 5.233r^2
r^2 = 83.74/5.233 = 16
r = sqrt(16) = 4
Therefore, d = 2(4) = 8 inches.