The first digit is the most restrictive, so we choose it first. We can choose the first digit any of 3 ways, 5, 6, or 7 We can choose the second digit any of the remaining 6 ways. We can choose the third digit any of the remaining 5 ways. We can choose the fourth digit any of the remaining 4 ways. Number of ways = 3*6*5*4 = 360 ways. Edwin