how do i solve this differential equation
dQ/dt = 50000 - (Q/160)??
you have $\displaystyle Q' = 5000 - \frac Q{160}$
$\displaystyle \Rightarrow Q' + \frac Q{160} = 5000$
now, find the integrating factor...here it is $\displaystyle e^{t/160}$, so we have
$\displaystyle e^{t/160}Q' + \frac 1{160} e^{t/160}Q = 5000e^{t/160}$
now finish up...