$\displaystyle \displaystyle \[A = {7^{15}} + {15^7}\]$

$\displaystyle \displaystyle \[B = {6^{16}} + {16^6}\]$

Hence

a) $\displaystyle \displaystyle \[A < B\]$

b) $\displaystyle \displaystyle \[A > B\]$

c) $\displaystyle \displaystyle \[A = B\]$

I remember evaluating something like that at school, but when was asked today unfortunately could not produce a reasonable answer