write the above three equations as:
[x] + {x} + [y] + {z} = 12.7 ............ (i)
[x] + {y} + [z] + {z} = 4.1 ............ (ii)
{x} + [y] + {y} + [z] = 2 ............. (iii)
(i) - (ii) - (iii),
u get
-2( {y} + [z]) = 6.6
==> {y} + [z] = -3.3
So, [z] = -4, {y} = 0.7
put these values in (iii),
{x} + [y] = 5.3
==> {x} = 0.3 and [y] =5
Put the values in (ii)
[x] + {z} = 7.4
==> [x] = 7 and {z} = 0.4