For this case we have the following equation:
u (t) = 12 • 2 ^ t / 3
We equate the equation for u (t) = 50.
We have then:
12 • 2 ^ t / 3 = 50
We clear the value of t:
2 ^ t / 3 = 50/12
log2 (2 ^ t / 3) = log2 (50/12)
t / 3 = log2 (50/12)
t = 3 * log2 (50/12)
t = 6.2 years
Answer:
After 6.2 years 50 acres of wetland are infested by an invasive plant species