The algae has an increase rate of 30% per day, this is an exponential increase, to calculate ot you have to use the following formula:
[tex]y=a(1-r)^x[/tex]
Where
a is the initial value
r is the growth rate
x is the time passed
y is the total growth after x time has passed
For this exercise, the initial number is 100 algae, the rate of growth is 0.3 and the time is 5 days, replace it in the formula:
[tex]\begin{gathered} y=100(1+0.3)^5 \\ y=371.293 \end{gathered}[/tex]
After 5 days you'll expect that the number of algae will gro by 371.293
