The prime factorizations of the numbers are
[tex]110 = 2\times 5 \times 11,\quad 40= 2^3\times 5,\quad 120=2^3\times 3\times 5[/tex]
The greatest common factor is composed by all common primes, taken with the lowest exponent possible. In this case, it will be
[tex]2\times 5 = 10[/tex]
