Solve for both systems: 6x+z=67 and z+4x=45

z+4x=45

z+4x-4x=45-4x

z=45-4x

6x+z=67

6x+45-4x=67

2x+45=67

2x+45-45=67-45

2x=22

2x/2=22/2

x=11

z=45-4x

z=45-4(11)

z=45-44=1