The logic here is
$$25^2-5^2=625-25=600$$
$$27^2-3^2=729-9=720$$
The top number is the difference of square of bottom left number and bottom right number.
Let the required number = a
Similarly, $$a^2-9^2=880$$
$$\Rightarrow$$ Â $$a^2-81=880$$
$$\Rightarrow$$ Â $$a^2=961$$
$$\Rightarrow$$ Â $$a=31$$
$$\therefore\ $$Required number = 31
Hence, the correct answer is Option C
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