It's a more interesting question if it's a multiplication, though going by the answer choices, that's not what's intended. But if you're asked the value of:

\((24 + 5\sqrt{23})(24 - 5\sqrt{23})\)

there's quite a nice solution using the difference of squares pattern twice:

\((24 + 5\sqrt{23})(24 - 5\sqrt{23}) = 24^2 - (5^2)(23) = 24^2 - (25)(23) = 24^2 - (24+1)(24 - 1) = 24^2 - (24^2 - 1) = 1\)

As for the question in the original post, the expression is clearly equal to 48, so there must be some kind of mistake somewhere.

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