Answer:
The number of bacteria after
will be 
Step-by-step explanation:
Given the initially 30 bacteria present in the culture.
Also, the number of bacteria got doubled every hour.
So, using the equation

Where
is number of bacteria after
hours.
is bacteria present initially.
is the common ration, in our problem it is given that bacteria doubles every hour. So, 
And
is the number of hours. In our problem we need amount of bacteria at the end of
hours. So, 
Plugging values in the formula we get,

So, number of bacteria after
will be 
Skylar went 13ft per second
Rodrigo went 13 1/2 ft per second
So, 1/2 a ft per second
20% of food is eater. 1 divided by 5 is 0.2. You move the decimal 2 unites which would be 20.
1 coin is 4 ways
2 coins is 4*3 ways
3 coins is 4*3*2 ways
4 coins is 4*3*2*1 ways
so total is 4+12+24+24=64 sums
How much part can sally paint in an hour ?
a ÷ 7 = a/7
And what about Steve ?
a ÷ 9 = a/9
Where, a is the total area of the room.
So, let the time taken by both of them to paint the room together be 't'
So,
t(a/7 + a/9) = a
t(9a/63 + 7a/63) = a
t(16a/63) = a
t = 63/16 ≈ 4 hr