Let the total amount be x.
Insurance =15%
Shopping + household =55%
Thus, the invested percentage is 15+55=70%.
30% is the remaining amount.
According to the problem, Sonali saves Rs. 12,750.
Therefore, 30% of x =12750
⇒30100×x=12750
⇒x=42500
Thus, the monthly income of Sonali is Rs. 42500.