This problem is about combined operations. We have a square power, a subtraction and whole products.
To solve this we can use PEMDAS which is an strategy to remember the order of operations, that is, Parentheses, Exponents, Multiplication-Division, Addition-Subtraction, that's the right order to solve.-
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According to PEMDAS, we solve the power first:
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Then, we solve multiplications:
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Finally, we subtract:

Therefore, the given expression is equal to 240.
Just remember, PEMDAS dictates the right order to use operations.