The new numbers after subtracting remainders are:

280-4 = 276

1245-3 = 1242

Prime factors of 276 = 23 × 3 × 2

Prime factors of 1242 = 2 × 3 × 3 × 3 × 23

Therefore HCF of 276 and 1242 is: 2 × 3 × 23 = 138

Hence the greatest number which divides 280 and 1245 leaving remainder 4 and 3 respectively is138