x - John's shoe size
Two people in the family wear shoe size 6, but John's shoe size is not 6.
The shoe sizes in the family:
6, 6, x
The range is the difference between the highest and the lowest value. The range is 4.
There are two possibilities:
1. John's shoe size is the biggest:
\(x-6=4 \\
x=4+6 \\
x=10\)
However, his shoe size is not 10, so it's impossible.
2. John's shoe size is the smallest.
\(6-x=4 \\
-x=4-6 \\
-x=-2 \\
x=2\)
John's shoe size is 2.
