Equations for ages

This task is about using equations to find out people's ages.
Prisha and Nikau were writing equations for the ages of people in their families.
Write an equation for each problem and use it to find the person's age.
Simone      Nick
a)
Prisha said that if you doubled her sister's age and added 5 the result would be 25.
 
i)   Complete this equation to find her sisters's age (s). ____________________ = 25
 
ii)   How old is Prisha's sister? ____________________
 
b)
Nikau said that his sister is 4 times as old as his brother, and together their ages add to 20.
 
i)   Complete this equation to find his brother's age (b). ____________________ = 20
 
ii)   How old is Nikau's brother? ____________________
 
c)
If you multiplied Prisha's father's age by 4 and subtracted 84, the answer is the same as if you doubled her father's age.
 
i)    Write an equation to find her father's age (f). ____________________
 
ii)   How old is Prisha's father? ____________________
 
d)
Nikau's mother was 30 when he was born. She is now 3 times as old as Nick.
 
i)    Write an equation to find Nikau's age (n). ____________________
 
ii)   How old is Nikau's mother? ____________________