> Still I failed to convince eval() to back my string to original numbers,
> but some folks're talk 'bout ASCII codes

The point is that in ruby 1.8 something like ?( denoted the character
'(' but this really is only a fixnum (40) -- as it was already
described by others.

The task is: you have
the following symbols/numbers

irb(main):002:0> p ??, ?-, ?*, ?), ?(
63
45
42
41
40

the operations *, - (with -- being +)
and parentheses.

Use this to build any number.

E.g. 1:
irb(main):004:0> eval('?)-?(')    # ~~ 41 - 40
=> 1

This is something slightly different than recoding a decimal number to
base-5 and using symbols instead of digits.

It took me some time to figure this out myself. It was really a nice
idea and an excellent quiz.