Answer:
12/30
Step-by-step explanation:
So we know that the denominator-numerator=18
And we also know that it's equal to 4/10 or 2/5.
Soooooooooooooo the most easiest is just to trial and error: 12/30
But I don't really know the more complex formula...
Answer:
It is 
Step-by-step explanation:
the four is multiplied 5 times
$819.20 is the answer considering each time the units increase by fours, it adds $204.80
The equations would be 5000(1+0.02)^3 and the answer is $5306.04