Let's take a peek at the denominators first off, and do a "prime factoring" on them.
25 = 5 * 5
27 = 3 * 3 * 3
45 = 3 * 3 * 5
the numbers in bold are repeated there more than once among the factors, and therefore we'll use them once, so our LCD will be 5 * 5 * 3 * 3 * 3, or 675.
25 = 5 * 5
27 = 3 * 3 * 3
45 = 3 * 3 * 5
the numbers in bold are repeated there more than once among the factors, and therefore we'll use them once, so our LCD will be 5 * 5 * 3 * 3 * 3, or 675.