Answer:
Let x be the number of silver medals.
As there were two more gold medals than silver ones, gold medals are x+2
We also know that the number of bronze medals was 4 less than the sum of gold and silver, so if there are x + 2 of gold and x of silver, there are x+x+2-4 of bronze.
Now, we can do an equation, as we know there were a total of 28 medals:
x + x + 2 + x + x + 2 - 4 = 28
And we isolate x:
4x = 28
x = 28/4 = 7
There were 7 silver medals, so there were 9 gold ones (7-2) and 12 of bronze (9+7-4).