Question 1039862
{{{system(y=-.2t^2+6.3t+42.9,0<=t<=24)}}}


6:30 AM  is  {{{6.5=t}}}.
{{{y=-0.2(6.5)^2+(6.3)(6.5)+42.9}}}
{{{highlight(y=75.4)}}}


You have two ways to find the maximum temperature and when it will be expected.
Either find the roots using general formula for quadratic equation and find the middle t
value and evaulate y for this t;  or put the y=quadraticExpression into standard form to read the vertex directly.
YOU try either of those.  Tell if you have trouble.


Maximum y is at t=15.75 hours.



--
Keep on working with it.  You may have the right idea.  Note that your given expression is for a parabolic function y=-0.2t^2+6.3t+42.9, and when you convert into standard form and graph it, this appears
{{{graph(400,400,-4,35,-4,100,-0.2x^2+6.3x+42.9)}}}