If=then

A

By comparing L.H.S and R.H.S

x - y = -1 -------- i

2x – y = 0 -------- ii

2x+ z = 5 --------- iii

3z + w =13 ------- iv

Using i in equation ii

x = -1 + y

ii becomes, -2 + 2y –y = 0

y = 2

x = 1

Putting x in iii

2 + z =5

z = 3

Putting z in iv

9 + w = 13

w = 4