Given:
Teddy has two sisters. One of them is 3 years younger than Teddy, the other one is 7 years younger than her only brother.
To find:
The age of older sister at the time when the younger sister was born.
Solution:
Let the age of Teddy be x.
One sister is 3 years younger than Teddy.
Age of one sister = x-3 years
The other one is 7 years younger than her only brother. It means other sister is 7 years younger than Teddy.
Age of other sister = x-7 years
Clearly (x-3) > (x-7). So, difference between the ages of sisters is



Therefore, the age of older sister is 4 years when the younger sister was born.
Okay, this is a written proof so what you have to do is list the steps. I am going to try my best to solve this problem...
Answer:
The maximum value of N-M will be 792
Step-by-step explanation:
For N - M to be maximum
N must be very large and M must be very small
largest 3 numbers occur in 900's and smallest 3 digit numbers occur in 100's
so we need such an N which starts with 9 and ends with 1 so that on reversing it produces a number starting with 1.
If N = 901 , M will be 109
N - M = 792
This is the largest possible value of N - M
All other values of N-M will give a smaller value than 792.
3 groups of 2 tenths is 1.5