x ≡ 0 mod 2
x ≡ 1 mod 3
x ≡ 2 mod 5
x ≡ 3 mod 7
a. What is the smallest x?
b. What is the largest 4-digit x?
x = 52 + 210k, where k is any integer
10000/210 ~= 47.6
so the answer to part b is either 52+47*210 or 52+46*210.
52+47*210 = 9922
Since it is under 10,000, this is the answer