Simplify by combining similar terms:
         4--7

Reducing into simplest form
= = 2
= =5
= = 2x2 = 4
.^..  4- - 7 = 4x 2 -5 - 7 x 4
                           = 8 - 5 -28 
                           =  (8-28) - 5
                           = -20 - 5