Question

Find the greatest number that divides451, 328 and 673 leaving 1, 4 and 1,respectively as remainders.

Answer 1

You're looking for the largest number x such that

x ≡ 1 (mod 451)

x ≡ 4 (mod 328)

x ≡ 1 (mod 673)

Recall that

x ≡ a (mod m)

x ≡ b (mod n)

is solvable only when a ≡ b (mod gcd(m, n)). But this is not the case here; with m = 451 and n = 328, we have gcd(m, n) = 41, and clearly

1 ≡ 4 (mod 41)

is not true.

So there is no such number.