Puzzle ZWPF 

Workings

Hint
The answer is a whole number less than 10.

Answer
3.

Checking that 3 works:
    3     3     3     3
    -  -  -  +  -  =  -
    3     2     4     12

    1 - 1.5 + 0.75 = 0.25

              0.25 = 0.25, which confirms that 3 is correct.

To deduce the answer directly from the question, we can multiply throughout by 12,

    *     *     *     *
    -  -  -  +  -  =  -
    *     2     4     12

to give:

   12 - 6* + 3* = 1*

        12 - 3* = 1*

             12 = 4*

              3 = *

As required.