--------------------------------                           
|         |value|number |      |                           
|         | per |  of   | value|                           
|         |unit | units |      |                           
--------------------------------                           
|nickel   | .05 |       |      |                           
--------------------------------                           
|quarter  | .25 |       |      |                           
--------------------------------                           
| total   |     |  30   | 5.50 |                           
--------------------------------                           
unknown = (total value - total number of units X           
          quarter value per unit) /                        
          (nickel value per unit - quarter value per unit);
nickel number of units = unknown;                          
quarter number of units = total number of units - unknown;