Answer:
24
Step-by-step explanation
Notice that Luke's real age is 12 times the number in the ratio, which is a simplified version of the original ratio, where they used division by 12 on both sides to get 3:2. Just do the opposite of division, which is multiplication, and multiply both sides of the ratio to get 36:24, which means that Jack is 24 years old!
Hope this helped you!