28 children were riding on the bus. At the bus stop 82 children got on the bus while some got off the bus. Then there were 30 children altogether on the bus. How many more children got on the bus than those that got off?
$$
\begin{array}{rcl}
x & = & \textrm{children that got off the bus} \\
y & = & \textrm{children that got on the bus} \\
28 & = & \textrm{initial number of children} \\
30 & = & \textrm{final number of children} \\
82 & = & \textrm{total number of children that got on the bus} \\
\end{array}
$$
So we can write down the equation:
$$
28 + y = 30 + x \Rightarrow y - x = 2.
$$
This equation means that there were 2 more children that got on the bus than those that got off the bus.