Hey kiddo..break it down
28 = 7 * 4
35 = 7 * 5
7 being common of the two. Common multiple is 7 * (4 * 5) = 140
28 = 7 * 4
35 = 7 * 5
7 being common of the two. Common multiple is 7 * (4 * 5) = 140