A=P+Prt

solve for t

I don't know if it is either

t= (a-p)/pr
or
t=-(1/r)+(A/Pr)

or is it a completely different answer?

Thank you in advance!!!

A = P + Prt

A-P = Pr*t
t = (A-P)/(Pr)
It is also
t = A/(Pr) - 1/r

I'd go with the first, but you might have reasons to use the second.