Isabella is twice as old as Antonio. In 18 months, she will be 10 years old. How many months old is Antonio? Let's answer step by step:
First, we determine that Isabella will be 10 * 12 = 120 months old at age 10, to find a number to compare her age to Antonio's with. Then we subtract the 18 months from the total of 120 months to find 120 - 18 = 102 months, which is the age Isabella is currently. Since at 102 months old Isabella is twice as old as Antonio, we take 102 / 2 = 51 months as Antonio's age. The answer: 51.