_ + _ = 8, _ + _ = 13, _ – _ = 6, _ + _ = 8.

Re-writing in modified form. Now we have a set of linear equations whose parameters are w, x, y, z.

……(i)

……(ii)

……(iii)

……(iv)

Solving these equations to find the values of x, y, w, z.

From (i)

From (iii)

From (iv) or

Using eq. (ii) to get

–x + 13 – x = 6

2 x = 7

Putting values of x in different equation

X = 3.5

Z = 3.5 from (iv)

Y = 8 – 3.5 = 4.5 from (i)

W = 13 – 3.5 = 9.5 from (iii)