What does it mean to take the exclusive OR of the three numbers $0, 2, 1$? This question asks about the exclusive-OR'ing of several numbers, each of which can assume more than two values (that is, more than $0$ and $1$).

What does this mean?  I did a Google search and found information on the ternary exclusive-OR, but that still involves $true$ and $false$ values, not $0, 1, 2, 3, ...$

Any ideas?
Taking them bitwise, which is probably what is intended, you have $00 \oplus 10 \oplus 01=11$
Exclusive-OR, or XOR in short, is an operation which will return true if an odd number of its inputs is true. It iwll return false if an even number of its inputs is false.

For example, an input of TTFTFFT will give false since there are 4 T's.

an input of TTTFFFFFFFF will be true since there are 3 T's.

Hope this helps. :)