Let's start by using algebra.

Let's say that the total number of people at the opening ceremony is "x".

We know that 28% of the people were men, so we can write:

0.28x = number of men

We also know that the number of men was 220 fewer than the number of women and children:

(number of women and children) - (number of men) = 220

We can also use the ratio given to us to represent the number of women and children:

Letting the number of women be 2y and the number of children be y, then:

(number of women and children) = 3y

Substituting this into the equation above, we get:

3y - 0.28x = 220

Now we have two equations with two unknowns. We can solve for y and x.

Multiplying the first equation by (3/7) to get the number of women and children in terms of x , we get:

(3/7)(0.28x) = 2y

Simplifying, we get:

0.12x = 2y

Substituting this into the equation we got earlier, we get:

3y - 0.12x = 220

We can now substitute 0.12x for 2y in the above equation to get:

3(0.12x) - 0.12x = 220

0.24x = 220

x = 916.67 (rounded to two decimal places)

So there were approximately 917 people at the opening ceremony.

Now we can use either of the two equations we got earlier to find the number of children. Let's use:

3y - 0.28x = 220

Substituting x = 916.67, we get:

3y - 0.28(916.67) = 220

3y = 466.67

y = 155.56 (rounded to two decimal places)

So there were approximately 156 children at the opening ceremony.