First find the factors of each number

Factors of 28: 1,2,4,

Factors of 77: 1,

What is the highest factor COMMON to both - answer -

I hope this helps

Factors of 28: 1,2,4,

**7**, 14, 28Factors of 77: 1,

**7**, 11, (you can go further, but there is no point as you have reached the highest COMMON factor)What is the highest factor COMMON to both - answer -

**7**I hope this helps