Answer:
210
Step-by-step explanation:
10+10+1=21
21 x 10=210
I am not sure exactly what you are looking for is this problem. Are you given choices from which to choose?
The empty set is a set with no numbers. Therefore, you should look for a set that doesn't have any elements.
We have,

Introduce variable
such that 
The sum
is therefore 
So,
(sadia's age)
(father's age)
Hope this helps :)
Answer:
1.dividing
2.to
Step-by-step explanation:
hope it helps