RPN:
3*5^(4-2)+6
Operands are shifted to output. So ... shift 3, stack *, shift 5,
stack ^ (stack higher prec), stack (, shift 4, stack -, shift 2,
pop - and output it, destroy (), pop ^ and output it, pop *
and output it, stack +, shift 6, pop + and output it. Done!
The final answer is
3542-^*6+
Push 3, 5, 4, 2; pop 2 and 4, push 4-2 = 2; pop 2 and 5, push 5^(2) = 25; pop 25 and 3, push 75; push 6; pop 6 and 75, push 75+6 = 81.