Okay, read all of this first and then read is again but slowly (if needed). 1st Pattern : 4 squares. 2nd Pattern: 7 Squares. 3rd Pattern : 10 Squares. As the pattern progresses, the number of squares increases by 3 each time. What we do is we get the number the squares added each time and stick an n on it as the number of squares goes up 3 each time for each pattern, so the first bit of the expression is 3n. What you do next is you get the number of squares (4, 7, 10...) and you take away 3n (n being the pattern number) so 4-(3*1), 7-(3*2), 10-(3*3)... . You should notice that the answer to each subtraction is the same (1). This makes the nth term 3n+1 since the number of squares seems to always be 3 multiplied by the number pattern plus 1. You should notice that this expression is basically the 3 times table plus 1. Hopefully this helps. Take your time reading and understanding if necessary.If you don't get something, feel free to mention it.