I know that you can convert fraction to percentage without converting to decimal.
Ex:
2/5 = 2/5 * 20/20 = 40%
How about fractions with denominator that cannot be converted to 100
Ex: 2/13
Is there any way / formula to solve this without converting the fraction to decimal?
No. Note that $40\%$ simply means $\dfrac{40}{100}$. So, can you write $\dfrac2{13}$ as $\dfrac k{100}$ for some integer $k$? No, because$$\frac2{13}=\frac k{100}\iff200=13k.$$But $200$ is not a multiple of $13$.