GMAT Math

Can someone please clarify when to use this formulae; if the principal is P, interest is R and time the interest accrued is t;

Principal after time T = P(1+R)^t ; R in decimal.

My question is, I assume this formuale is only applicable to simple interest? Also, is this applicable to any "special" simple interest related questions or is it applicable to all simple interest problems?

If a question asks to find the principal P after 6 mos, which accrues 7% monthly interest,can this formulae be applied?

Can I say, Final P after 6mos = P(1 + 0.07)^6 ; (do we need to convert mos to yearly as in 6/12 ) ?

Unfortunately, I don't have a question to post but I remember having some difficulty trying to apply this to a problem and I remember reading this in the GMAT Flash cards. Appreciate anyones response.