40+(-z)=0
40-z=0
z=40-0
z=40
.
8.6-(-z)=0
8.6+z=0
z=0-8.6
z= - 8.6
(-z)-50.2=0
-z - 50.2=0
z+50.2=0
z= -50.2
-67+(-z)=0
-67 - z=0
z= - 67
40+(-z)=0
40-z=0
z=40-0
z=40
.
.
8.6-(-z)=0
8.6+z=0
z=0-8.6
z= - 8.6
.
.
(-z)-50.2=0
-z - 50.2=0
z+50.2=0
z= -50.2
.
.
-67+(-z)=0
-67 - z=0
z= - 67