To me, do the math using compatible number, means to estimate
7233 can round to 8000
and 84 can round to 80
now, this makes it easy, you can do it mentally, which is 100
In more detailed,
7233 can round to 7225
and 84 can round to 85
then, (not so obvious, but however) 85 times 85 equal 7225
so the compatible number of 7233 divided by 84, is 7225 and 85
I know it's a bit late, but hope it helps