Since we know x2 is equivalent to x times x we can automatically start by filling in the first two spaces with x. Then since we know that we're going to need two numbers that equal forty since it's part of the equation we can get two number that will also add up to 13x which is 8 and 5. We then get (x+8)(x+5). (Sorry lol this question is kind hard to explain over the computer.)
