Which situation is best modeled by the equation 11 + x = 28?

For example, let's say that you had a birth day party, and at the party, you had 11 people all ready bringing food, but you needed 28 people to bring food. And in this equation, "x" would represent the amount of people that  needs to come to bring food, and that 28 would then be the total.

We then do, 28 - 11 = 17.

And therefore, there would then have to be 17 people who would have to attend to bring food for the part. (end of example).

So this above would show and model on how to use these kind of equations in a real situation in a everyday life.

Could you make it more clear?