First we have to find the common ratio. We do this by dividing the second term by the first term.
ur first problem... 12/3 = 4...so the common ratio is 4
now we use the formula an = a1 * r^(n-1) n = term u want to find = 15 a1 = first term = 3 r = common ratio = 4 now we sub a15 = 3 * 4^(15 - 1) a15 = 3 * 4^14 a15 = 3 * 268435456 a15 = 805,306,368 <== ur 15th term
thats all there is to it...and, of course, u can always look on the internet for a geometric sequence calculator...to check urself...lol
