Change the subject of the formula S = P (1+rt) to t

So basically we want to get t by itself on one side

so s=p (1+rt)

divide both sdies by p

s/p=1+rt

subtract 1

(s/p) - 1=rt

divide by r

[ (s/p) - 1]/r=t

If we're changing the subject to t, we want to get t on it's own.

S = P (1 + rt)

Since we can't do anything with the parenthesis, we have to start with the division/multiplication. Divide both sides by P:

S = 1 + rt

P

Next we want to get rid of the 1, so subtract 1 from both sides:

S - 1 = rt

P

finally, divide both sides by r

(S/P) - 1 = t

r

so:

t = (S/P) - 1

r