Solve for both systems: 7z+4x=83 and z + 4x = 53

z + 4x = 53

z + 4x-4x = 53-4x

z= 53-4x

7z+4x=83

7( 53-4x)+4x=83

7( 53) (7)(-4x)+4x=83

371-28x+4x=83

371-24x=83

371-371-24x=83-371

-24x=-288

-24x/-24=-288/-24

x=12

z= 53-4x

z= 53-4(12)

z= 53-48=5