I start by finding the LCM (lowest common multiple) of 5, 9, and 7, which is 315. Then, to calculate the top number, I divide 315 by the denominator to determine how many times I need to multiply the numerator. For 5, it's 63, giving us a numerator of 126. For 9, it's 35, giving us a numerator of 140. For 7, it's 45, giving us a numerator of 135. I then compare the numbers to find the answer.
