Question 241422
There isn't enough information to know what
year it's starting at.
I'm assuming that {{{t}}} is the number of years 
that have passed, and {{{t = 0}}} is the 1st year
{{{F(t) = 115.1*.9352^t + 900}}}
{{{F(0) = 115.1*.9352^0 + 900}}}
{{{F(0) = 115.1*1 + 900}}}
{{{F(0) = 1015.1}}} million acres the 1st year
When does the land total {{{910}}} million acres?
{{{F(t) = 910}}}
{{{910 = 115.1*.9352^t + 900}}}
Subtract {{{900}}} from both sides
{{{10 = 115.1*.9352^t}}}
Take the log to the base {{{10}}} of both sides, noting that
{{{log(10) = 1}}}
{{{log(a*b) = log(a) + log(b)}}}
{{{log(a^b) = b*log(a)}}}
{{{1 = log(115.1) + t*log(.9352)}}}
{{{1 = 2.061 - .0291t}}}
{{{.0291t = 2.061 - 1}}}
{{{.0291t = 1.061}}}
{{{t = 36.46}}}
and
{{{.46*12 = 5.52}}}
{{{t}}} is about equal to 36 years and 5 months.
Sometime in the 5th month of the 36th year, 
the farm acres drops below {{{910}}}