So you are going to multiply the fractions by 10,000 to find the amount of money used on that item.
1/2 x 10,000 = 5,000   - FOOD 
1/4 x 10,000 = 2,500   - BEVERAGES
1/10 x 10,000 = 1,000  - DECORATIONS
5,000 + 2,500 + 1,000 = 8,500 
10,000 - 8,500 = MONEY SPENT ON STAFFING 
                          = 1,500