Let the number be x.

According to the question,

\( \Large 5x = 2x^{2} - 3 \)

=> \( \Large 2x^{2} - 5x - 3 = 0 \)

=> \( \Large \left(x-3\right) \left(2x+1\right) = 0 \)

\( \Large x = 3, -\frac{1}{2} \)

Thus, the required number is 3.