Two numbers are, respectively, $16\%$ and $30\%$ less than a third number. The ratio of the two numbers is:

Let the third number be $100$.First number = $16\%$ less than $100=100-16=84$ Second number = $30\%$ less than $100=100-30=70$ The ratio of the first number to the second number is:
$$\text{Ratio}=\frac{84}{70}$$
Dividing both numerator and denominator by their greatest common divisor, $14$:
$$\text{Ratio}=\frac{6}{5}=6:5$$