Solve for both systems: 13z+12y=109 and 4z + 4y = 36

4z + 4y = 36

4z-4z + 4y = 36-4z

4y = 36-4z

4y /4= 36-4z/4

y=9-z

13z+12y=109

13z+12(9-z)=109

13z+12(9) (12)(-z)=109

13z+108-12z=109

z+108=109

z+108-108=109-108

z=1

y=9-z

y=9-1=8