89z – 66z – -71z – -85 = -9

89z – 66z – -71z – -85 = -9

 

89z – 66z +71z +85 = -9

 

89z – 66z +71z      +85-85 = -9-85

(89 – 66  +71 )z      = -94

 

89-66+71 = 94

 

94z = -94

divide both sides by  94

 

z= -1