We'll start out allowing 0 to be a first digit then we'll count those and subtract. There are 5 positions for the 5 digits. Choose the position for the 2 in 5 ways. Choose the position for the 5 in 4 ways. There are three vacant positions remaining. Choose a digit to go in the leftmost vacant position 6 ways. Choose a digit to go in the middle vacant position 5 ways. Choose a digit to go in the rightmost vacant position 4 ways. That's (5)(4)(6)(5)(4) = 2400 We must now count the undesired ones, i.e., that begin with 0. We can consider these to be 4-digit numbers with digits from {1, 2, 3, 4, 5, 6, 7} that must include the digits 2 and 5. There are 4 positions for the 4 digits. Choose the position for the 2 in 4 ways. Choose the position for the 5 in 3 ways. There are two vacant positions remaining. Choose a digit to go in the leftmost vacant position 5 ways. Choose a digit to go in the rightmost vacant position 4 ways. That's (4)(3)(5)(4) = 240 Subtracting, 2400-240 = 2160 <--ANSWER Edwin