You know that it could grow to 6 inches in a week which is 7 days. Now, 24 days would be 3 weeks and 3 days. Multiply 6 by 21 which is the equivalent of three weeks. Then divide the number 6 by seven to know how much it could grow in a day. then multiply the quotient by 3 (cause that's the number of days left)
6*21 = 126
6/7 = 2.57
Add both of the answers.
=128.57
(hope this is right :)) )