First you had to remove parenthesis first.

Multiply by the numbers.

Final answer 



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Measure of x is 74 degrees
Answer:
Step-by-step explanation:
12n2+48n=−n3−64
Step 1: Subtract -n^3-64 from both sides.
12n2+48n−(−n3−64)=−n3−64−(−n3−64)
n3+12n2+48n+64=0
Step 2: Factor left side of equation.
(n+4)(n+4)(n+4)=0
Step 3: Set factors equal to 0.
n+4=0
n=−4