Answer is
x = -64
y = -63
z = -57
Step by step
the sum of the interior angles of a parallelogram is 360 degrees. The opposite interior angles are equal.
60 = -y -3
Add 3 to both sides
60 + 3 = -y -3 +3
Simplify
63 = -y or
y = -63
We know the sum of both angles = 60 + 60 = 120
360 - 120 = 240
So the sum of the other two angles = 240
Since the opposite interior angles are equal they will each equal half, or = 120.
-2z + 6 = 120
Subtract 6 from both sides
-2z +6 -6 = 120 -6
Simplify
-2z = 114
Divide
-z = 57
z = -57
Check your work
-2z + 6 = 120
-2(-57) +6 = 120
114 + 6 = 120
120 = 120 ✅
-2x -8 = 120
Add 8 to both sides
-2x -8 +8 = 120 +8
Simplify
-2x = 128
Divide
-x = 64
x = -64
Check your work
-2x -8 = 120
-2(-64) - 8 = 120
128 -8 = 120
120 = 120 ✅