Julio's father is 4 times as old as Julio. The sum of their ages is no less than 55.
What is the youngest age Julio can be?
let's make a key:
Julio's age = x
Julio's father's age = 4x
the sum of their ages is no less than 55, so it's equal or more than 55. we have this inequality:
4x+x > 55
so the youngest Julio can be is 11 years old.