If you have a quantity h increasing by 125% every 5 hours, but 20 units are subtracted every hour, how would you write the differential equation for the rate of change of h?

Is it

dh/dt = c*h -20*t where c is a constant and t is the number of hours

or is it just

dh/dt = c*h -20

?

And would you solve them using sep. of variables, integrating factor or another method?

Thank you for any help.