Thank you for the warm welcome. I am now wondering where i should ask my questions at, which forum. Its pre-algabra so i dont want to bother anyone with some really basic things that they dont care to see/ For example, the question i have right now is a method for simply finding a composite number. Im going through the khan Academy exercises and they have this...... Which of these numbers is composite? 71, 79, 59, 91, 83 Now i know what composite is ( a number that has a factor of itself, 1 and other numbers ), i know what prime is ( a number with a factor of 1 and itself ). But the thing i cant ask anyone is that i dont understand their method at arriving at the answer. The only way i can think to figure the answer is to do this for every number... 71/1 = 71 71/2 = 35r1 71/3 = 23r2 71/4 = 17r3 71/5 = 14r1 71/6 = 11r1 71/7 = 10r1 How long do i keep this up before i can say, yes this is a prime number and move on to the next number. The answer is given and its 91 is composite cause 1x71= 71 and 7x13= 91. But something tells me im going about it all wrong. thank you for any advice.