Solve for both systems: y+3z=40 and 7y- 3z = 16

y+3z=40

y+3z-3z=40-3z

y=40-3z

7y- 3z = 16

7(40-3z)- 3z = 16

7(40) (7)(-3z)- 3z = 16

280 -21z- 3z = 16

280 -24z= 16

280 -24z-280= 16-280

-24z=-264

-24z/-24=-264/-24

z=11

y=40-3z

y=40-3(11)

y=40-33=7