No, it does not always have to be a decimal although it is more common to have one.
Lets get started :)
The ratio of juice is as follows:
orange : mango : apple
3 : 5 : 4
↑
35 bottles
5x = 35

5 and 5 cancels out
x = 7
3x + 5x + 4x = total
Subsitute the value you go for x, x = 7
3(7) + 5(7) + 4(7) = total
21 + 35 + 28 = 84
Total of
84 bottles of juices :)
Your final answer will be
option D
$135 + $15x is greater than or equal to $300
On the left the function goes to infinity
on the right it goes to-infinity