Using decode to check for negative and positive values

You can use 'sign' with a decode. Sign will return -1 for any negative, 0 for 0, and 1 for any positive:

select decode(sign(money_return), -1, abs(money_return), 
                                   1, money_return*10, 
                                   money_return) 
from cash_t;

You need case statement

select CASE 
 WHEN money_return < 0 THEN abs(money_return)
 WHEN money_return > 0 THEN money_return*10
 ELSE money_return END money_return from cash_t;