Mia is three years older than twice her sister brooks age. The sum of their ages is less than 30. What is the greatest Brooke could be

Let Mia's age be m and her sister's age be x m=2x+3 2x+3+x=less than 30 For greatest age we need to take largest number. 3x+3=29 x=26/3 But the options are all in whole numbers, so if 3x+3=27 then x = 8