hi guys , have mind blank on how to best do this code in math than use a lookup

Code:
        if val < 6  AND Menu_Select = 211 then   lookup val,[0,2,4,8,16,32],val 
        if val =>6  and val <= 11 and Menu_Select = 2112 then  lookup val-6,[0,2,4,8,16,32],val
        if val =>12 and Menu_Select = 2113 then lookup val-12,[0,2,4,8,16,32],val