This equation is telling you to subtract the value of f(x) from the value of g(x).
f(x)= x + 2
g(x) = 3x + 5
so x + 2 - 3x -5 = -2x-3
I pick cancer and the growth rate is 6% per day then 2 weeks by (14 days) the growth of cancer is now 84% (6x14)
the table is two weeks later
hope this helps