Question 1132151
b = Bon's present age
s = Sonia's
:
Write an equation for each statement

Bon wants to take an early retirement in 10 years when he will be twice as old as his daughter Sonia.
b + 10 = 2(s+10)
b + 10 = 2s + 20
b = 2s + 20 - 10
b = 2s + 10
:
Sonia is 25 years younger than her father.
s = b - 25
:
In the 1st simplified equation, replace s with (b-25)
b = 2(b-25) + 10
b = 2b - 50 + 10
b = 2b - 40
40 = 2b - b
b = 40
:
 how old is Bon now?
40 yrs old
 How old will he be when he retires? 
40 + 10 = 50 yrs old
:
;
Check this
Sonia's age: s = 40-25 = 15 yrs: Check in the equation, b = 2s + 10
40 = 2(15) + 10
and
In 10 yrs he will 50, she will 25