$$ {\textbf{Step -1: Find the amount Shreya will get}} $$
$$ {\text{Ratio of ages = }}\dfrac{{15}}{{12}}{\text{ = }}\dfrac{5}{4} $$
$$ {\text{Therefore, mother wants to divide Rs}}{\text{.36 in a ratio of 5:4}}{\text{.}} $$
$$ {\text{Terms of }5:4\text{ are 5 and 4}}{\text{.}} $$
$$ {\text{Sum of these terms }= 5 + 4 = 9} $$
$$ {\text{Shreya will get }}\dfrac{5}{9}{\text{ of the total money}}{\text{.}} $$
$$ {\text{Amount that Shreya will get = }}\dfrac{5}{9} \times{\text{ 36 = 20 Rs.}} $$
$$ {\textbf{Step - 2: Find the amount Bhoomika will get}} $$
$$ {\text{Bhoomika will get }}\dfrac{4}{9}{\text{ of total amount}}{\text{.}} $$
$$ {\text{Amount that Bhoomika will get = }}\dfrac{4}{9} \times{\text{ 36 = 16 Rs.}} $$
$$ {\text{So, Shreya and Bhoomika will get Rs}}{\text{.20 and Rs}}{\text{.16 respectively}}. $$
$$ {\textbf{Hence , Shreya and Bhoomika will get Rs}}{\textbf{.20 and Rs}}{\textbf{.16 respectively}}. $$