Answer: $1.50
Step-by-step explanation:
Cost price of watermelon = $1.25
Profit percent = 20%
Profit = Profit percent × Cost price
= 20% × $1.25
= 20/100 × $1.25
= 0.2 × $1.25
= $0.25
Selling price = Cost price + Profit
Selling price = $1.25 + $0.25
Selling price = $1.50
They should charge $1.50 for the watermelons
Answer: 
Not a factor because there is a remainder.
Step-by-step explanation:
Let's use synthetic division to solve this..
-1 ║ 2 | 4 | -2 | -8
║ | -2| -2 | 4
║ 2 | 2| -4 | -4

PS: if anyone knows a better way to do a synthetic division chart please let me know.