Answer:
I am not sure how about you figure it out maybe study
This would be A because $100 is the initial amount, and you are adding the amount that arises after (d) days. Since you are adding, it will be the sum. B says product, so you can rule it out. D says difference, so you can rule that out as well. C would be adding the days, not the amount earned each day.
4/3
Remember if two lines are perpendicular, the product of their slopes are -1
Distance Formula: 
Point 1: (9,0)
Point 2: (5,-8)
D = sqrt[ (5 - 9)^2 + (-8 - 0)^2 ]
D = sqrt[ (-4)^2 + (-8)^2 ]
D = sqrt[ 16 + 64]
D = sqrt(80)
Hope this helps!