Fill the blanks for question mark 3 : 10 = 12 : ? = ? : 50.

3 : 10 = 12 : ? can be written in the form of an equivalent fraction$\frac{3}{10}=\frac{12}{?}$, In two equivalent fractions numerator and denominator are multiplied by the same number to get the numerator and denominator of the second fraction. Here numerator $3$ of the first fraction becomes $12$ by multiplying it by 4 and the same number 4 must be multiplied with the denominator 10.
$\frac{3}{10}=\frac{3\times 4}{10\times 4}=\frac{12}{40}$
So the denominator, in this case, is 40.
Also 3: 10 = ?: 50 can be written in the form of an equivalent fraction$\frac{3}{10}=\frac{?}{50}$, With the same explanation as in the above equivalent fraction here denominator 10 becomes 50 by multiplying 10 with 5 accordingly 3 multiplied with 5.
$\frac{3}{10}=\frac{3\times 5}{10\times 5}=\frac{15}{50}$
So the numerator, in this case, is 15.
So question marks blank filled by 40 and 15 respectively.