Im new here, and i'm not sure where to put this Q,
I was studying for the AMO, and I came across a problem in the 2004 AIMO which has me completely stuck ...
A new binary operation ? defined on all positive x and y, satisfies the following conditions:
i x?x = x+2
ii x?y = y?x
iii x?(x+y) = x+y
Given the above, find 11?8
please explain how to do this, i have been to other forums, and unless I ask, they just give a number.