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Answer:
a = -5
Step-by-step explanation:
a = 1/2(-10) + 3^2 - (-1) - 10
a = -5 + 3^2 - (-1) -10
a = -5 + 9 - (-1) - 10
a = 4 - (-1) - 10
a = 4 + 1 - 10
a = 5 - 10
a = -5
x = -1y = 3
z = -10
a = -5