Kids grow up fast these days!
Algebra
Level
1
Lily is twelve years old and her brother, Percy, is eight. Their mother, Laura, was twenty-seven when Percy was born. How old will Laura be when the sum of Lily and Percy's ages is forty?
The answer is 45.
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Let Laura's age be x,
Percy's age = Laura's age - 27
Percy's age = x - 27
Lily's age = 4 + Percy's age
Lily's age = x - 23
So, as Lily's age + Percy's age = 40
x - 23 + x - 27 = 40
2x - 50 = 40
2x = 90
x = 45
Hence Laura's age is 45, when Lily and Peter's ages sum to 40.