Which two equations below could you solve to find d, the number of days it takes the water lily population to double? 2 = 3.915(1.106)d 7.830 = 3.915(1.106)d 7.830 = 3.915(2)d 2 = 1.106d

This is the concept of algebra, suppose the initial number was x, and the new number is 2x. The constant rate of growth is r and time is D, the function representing growth will be given by:
2x=x(r)D
from our choices the equations that represents the information above will be:
7.830=3.915(1.106)D
and
7.830=3.915(2)D
this is because from both equations we see the initial number was 3.915 and doubled to 7.830

I've set up a conversion equation:
You can just say it out loud what you're trying to do and that will help you write out your ratios.
45.9 grams per 1 ball
1 ounce per 28.35 grams
We have 12 balls
45.9
g
b
a
l
l
⋅
1
o
z
28.35
g
⋅
12
(
b
a
l
l
)
45.9
g
b
a
l
l
⋅
1
o
z
28.35
g
⋅
12
(
b
a
l
l
)
=
45.9
⋅
12
28.35
≈
19.4
o
z