That is true because you are still dividing x by three either way
Let number of plastic containers collected by fourth grade= x
Then number of plastic containers collected by fifth grade students=x-216
OR
If number of plastic container collected by fifth grade is y
then number of plastic container collected by fourth grade=y+216
So, we can write it as follows
⇒ number of plastic containers collected by fourth grade= number of plastic containers collected by fifth grade +216
10.2
and
5.6
and
7.9
Hope this helped :)