find highest common factor 12 & 20
It's 4. The factors of 12 are: 1,2,3,4,6,12. The factors of 20 are: 1,2,4,5,10,20.
\(D_{12}=\{1,2,3,\boxed{\underline{4}},6,12\} \\ D_{20}=\{1,2,\boxed{\underline{4}},5,10,20\} \\ \\ \text{Answer:4}\)
