Problem: the sum of ages of 5 children born at the intervals of 3 years each is 80 years . what is the age of the youngest child ?
Rationale: "let the ages of children be x , ( x + 3 ) , ( x + 6 ) , ( x + 9 ) and ( x + 12 ) years . then , x + ( x + 3 ) + ( x + 6 ) + ( x + 9 ) + ( x + 12 ) = 80 5 x = 50 x = 10 . age of the youngest child = x = 10 years . e )"
annotated_formula: subtract(subtract(divide(80, 5), 3), 3)