Find the common denominator of 3 and 12 which would be 12. Then we add the 2 fractions together to get 9/12. Now we know that 9/12 of the guests chose chicken and beef. We also know that 69 guests is equivalent to 3/12 which can be simplified down to get 1/4. So now we can do 69x4 to get 4/4 which is also 12/12, the amount of guests . 69x4 is 276 Your final should be 276.
