1. - 9x=16-y

12x=-5-y

-9x=16-y equation 1

12x=-5-y equation 2

x=-5-y:12 from equation 2

substitute this x in equation 2

so

-9 (-5-y:12) = 16-y

15+3y=64-4y

7y=49

y=7

and then substitute this value of y in equation (x=-5-y:12)

so x = - 5-7:12

x=-1

so y=7 and x=-1