Consider the 150 marigolds.
After the first month, 0.85*150 are left
After the second month, 0.85*0.85*150=
After the third month, 0.85*0.85*0.85*150 =
so After n months, marigolds are left.
in functional notation: is the function which gives the number of marigolds after n months
consider the 125 sunflowers.
After 1 month, 125-8 are left
After 2 months, 125-8*2 are left
After 3 months, 125-8*3 are left
After n months, 125-8*n sunflowers are left.
In functional notation: S(n)=125-8*n is the function which gives the number of sunflowers left after n months
marigolds are left after 3 months.
S(3)=125-8*3=125-24=121 sunflowers are left after 3 months.
Answer : equalizing M(n) to S(n) produces an equation which is very complicated to solve algebraically.
A much better approach is to graph both functions and see where they intersect.
Another approach is by trial, which gives 14 months
which are close numbers to each other.