Question 134857
Given: {{{R= -0.075t+3.85 }}}

At some year, the time will get below 2.8 minutes

{{{2.8 > -0.075t+3.85 }}}
{{{(2.8-3.85) > -0.075t }}}
Remember to swap the sign when multiplying or dividing by a negative
{{{ ((-1.05)/(-0.075)) < t }}}
{{{ 14 < t }}}

So any year > 1930 + 14 will do it
{{{ t > 1944 }}}