Answer:
2/3
Step-by-step explanation:
42/63 = 2/3
15/22.5 = 2/3
It's 120*0.42 = 50.4 so 50.4 is the answer
The way to solve this question is to essentially reverse the equation I used in the other answer.
I would solve this with some theoretical values. If you start with 3, how long would it take for it to triple, or reach 9.
the equation would look like 9 = 3(2)^t/6, note how the instead of 1/2 it is now 2 in the parenthesis, as it doubles every 6 hours rather than halves every amount of hours.
When placed into an algebra calculator, the answer should be about 9.5 hours
-16t^2+400=0
16t^2=400
take square root on both sides.

4t=20
t=20/4
t=5