I believe your answer is D. 77.
<span>let x be the interval, then:
186 = 50 + 3 + (3+x) + (3+2x) + (3+3x) + (3+4x) + (3+5x) + (3+6x) + (3+7x)
186 = 74 + 28x
x = 4
Eldest son age = 3+7x = 3+28 = 31.</span>
1 carton : 8 boxes for 2.80 = 2.80/8 = 0.35 per box (All natural juice)
1 carton : 6 boxes for 1.98 = 1.98/6 = 0.33 per box (Just juice)
difference between the 2 is 0.02 (2 cents)
if she paid 7.92 for x cartons of Just Juice, 7.92 / 0.33 = 24 boxes...and there are 6 boxes per carton.....24/6 = 4 cartons were bought for $ 7.92
price for same number of juice boxes of All Natural juice is :
24 * 0.35 = $ 8.40
13!=13×12×11×10×9×8×7×6×5×4×3×2×1
=6,227,020,800
