Factors of $${\mathtt{89}}$$: $${\mathtt{1}}$$ , $${\mathtt{89}}$$
Factors of $${\mathtt{113}}$$: $${\mathtt{1}}$$ , $${\mathtt{113}}$$
Factors of $${\mathtt{73}}$$: $${\mathtt{1}}$$ , $${\mathtt{73}}$$
The number they all have in common is $${\mathtt{1}}$$ which means the greatest common factor of $${\mathtt{89}}$$, $${\mathtt{113}}$$, and $${\mathtt{73}}$$ is $${\mathtt{1}}$$.
Since 89, 113, and 73 are all prime numbers, their greatest common factor is 1.
Factors of $${\mathtt{89}}$$: $${\mathtt{1}}$$ , $${\mathtt{89}}$$
Factors of $${\mathtt{113}}$$: $${\mathtt{1}}$$ , $${\mathtt{113}}$$
Factors of $${\mathtt{73}}$$: $${\mathtt{1}}$$ , $${\mathtt{73}}$$
The number they all have in common is $${\mathtt{1}}$$ which means the greatest common factor of $${\mathtt{89}}$$, $${\mathtt{113}}$$, and $${\mathtt{73}}$$ is $${\mathtt{1}}$$.