If Leah is 6 years older than her sister, Sue,
and John is 5 years than Leah, and the total 
of their ages is 41. Then how old is Sue?

Let x = Sue's age

>>...Leah is 6 years older than...Sue...<<

So Leah's age is Sue's age plus 6 or (x+6)

>>...John is 5 years than Leah...<<

So John's age is Leah's age plus 5 or (x+6)+5

>>...the total of their ages is 41...<<

So Sue's age plus Leah's age plus John's age 
equals 41 OR

      x + (x+6) + (x+6)+5 = 41

Solve that and get x=8

So Sue is 8, Leah is 6 years older, or 14, 
and John is 5 years older than Leah, or 19.
Checking:  8+14+19 = 41

Edwin