Answer :
the formula should be I=Prt but whatever
if you had I=Prt then divide both sides by Pr to get I/(Pr)=t
if you want to use P=Irt, divide both sides by Ir to get P/(Ir)=t
if you had I=Prt then divide both sides by Pr to get I/(Pr)=t
if you want to use P=Irt, divide both sides by Ir to get P/(Ir)=t