Find the equivalent fraction of $$\dfrac {3}{5}$$, having:
denominator $$30$$
To have denominator $$30$$, we should find out $$30 \div 5=6$$
So, we must multiply numerator and denominator by $$6$$ to get the equivalent fraction :
$$\dfrac{3\times 6}{5 \times 6}=\dfrac{18}{30}$$