Answer
(a). $T=200e^{-0.11t}+20$
(b). $T=42.161$
Work Step by Step
$\ln \left(\frac{T-20}{200} \right)=-0.11t$
(a).
$\frac{T-20}{200} = e^{-0.11t},$
$T-20=200e^{-0.11t},$
$T=200e^{-0.11t}+20$
(b).
$t=20$
$T=200e^{-2.2}+20,$
$T=42.161$