Answer:
24 over 10
Step-by-step explanation:
I did it in my head
A) total cost is $14.99
b) total cost is $19.99
i did the work for you on a paper but i'm having trouble sending it on here. sorry man really wanted to help. /: i can send it to you anywhere else if you want

You can chose any three out of those four.
Hope that helped :)
7:3=8:x is like like 7/3=8/x
so 7x=24
24/7=x
x=~3.43