All of them in scientific notations

Scientific notation = M x 10^n.    M is a number between 1 and 10. n is a negative or positive integer

d) 0.091 = 9.1 x 10^-2

h) 30,600 = 3.06 x 10^4

i) 34.967 = 3.4967 x 10^4

D) 0.091 move the decimal to
the right two times so it’s
9.1 x 10^-2

H) move the decimal to the left 4 times
3.06 x 10^4

I) move the decimal to the left 4 times
3.4967 x 10^4

Not sure if there should be options listed, but here is an equation he should use:
f(t) = 3*2^t, where t= number of months since first observation.
or
f(t)= 3*2^(t-1), if the moment of observation is t=1

If this isn't an availabe option, plug in a few values for t (number of months) and make sure they match our values
Based on the first equation:
When t = 0 (when Roberto first observes the bacteria):
f(0) = 3*2^0 = 3*1 = 3
f(1)=3*2^1 = 3*2  = 6
f(2)= 3*2^2 = 3*4 = 12
and so on until...
f(43)=3*2^43 = 26,388,279,066,624 That's a lotta bacteria!