a boy in a blue uniform is standing next to a boy in red and a boy in yellow and they are holding baseball gloves.
Three boys hold baseball gloves.
There are three boys (a boy in blue uniform, boy in red boy in yellow) as they hold baseball gloves.
A boy in blue, next to a boy in red, and a boy in yellow, makes three boys in total. All of them are holding baseball gloves.
Three boys who hold baseball gloves are wearing blue, red and yellow uniforms.