Answer: Z=-5
Explanation:
we want to group Z on only one side of the equation
-18=Z-3+2Z
-18-Z-2Z=-3 (subtract Z and 2Z from both sides, to remove Z from one side and to move it to the other side)
-3Z=-3+18 (regroup Z and add 18 on both sides, to have Z on only one side)
-3Z=15 (add -3+18)
3Z=-15 (multiply both sides by -1 to get a positive Z)
Z=-5 (divide both sides by 3)