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Sally is 8 years older than john. John is 14 years older than Karen. If the sum of their ages is 90, how old are they?
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Let K be the Karen's age.
Then the John's age is (K+14) years, and Sally's age is (K+14)+8 = K + 22 years.
As the condition says, the sum of ages is 90, which gives you an equation
K + (K+14) + (K+22) = 90.
Simplify and solve for K:
3K + 36 = 90,
3K = 90 - 36,
3K = 54,
K = = 18.
Answer. Karen is 18 years old. John is 18+14 = 32 years old. Sally is 32+8 = 40 years old.
The lesson to learn from this solution:
1. First choose the major unknown reasonably.
2. Second, express other unknowns via the major unknown.
3. Then make an equation.
4. Then solve the equation.
It is the algorithm.