I'm pretty sure A, and C but I'm not very sure about B I hope that helped.
Answer:

Step-by-step explanation:
Given

Required
Find V when

Substitute
for r in 

Open bracket


Simplify the fractions

Let

So:




Answer:
Shira: x = 8
Samuel: m = 0
Step-by-step explanation:
Shira's mistake was that she subtracted 2 from both sides instead of adding to on both sides.
Correct Solving:
2x - 2 = 14
Add 2 to both sides;
2x = 16
Divide both sides by 2;
x = 8
Samuel's mistake was that when he distributed -2 to 8m and 8 he put the wrong sign for -2 * 8.
Correct Solving:
-2(8m + 8) = -16
Distribute;
-16m - 16 = -16
Add 16 to both sides;
-16m = 0
Divide both sides by -16;
m = 0
$9.47
I just multiplied the total by the refund percentage to get that number. It’s just like finding a tip.
Answer:
let x=rate of the rowing team in still water
x+4=rate of the rowing team with current
x-4=rate of the rowing team against current
travel time=distance/rate
..
90%2F%28x%2B4%29=10%2F%28x-4%29
90x-360=10x+40
80x=400
x=5 rate of the rowing team in still water=5 mph