1. **State the problem:** We have a group of students with preferences for three types of crisps: ready salted, cheese and onion, and salt and vinegar. We know the number of boys and girls who prefer certain flavors, and we want to find the total number of students who like ready salted best. 2. **Given data:** - Total boys = 42 - Boys who like cheese and onion = 17 - Girls who like ready salted = 15 - Total students who like salt and vinegar = 39 - Girls who like salt and vinegar = 23 3. **Find:** Number of students who like ready salted best. 4. **Step 1: Find the number of girls.** Total students = boys + girls We know boys = 42 Girls = total students - 42 (unknown total students for now) 5. **Step 2: Find boys who like salt and vinegar.** Total salt and vinegar likers = 39 Girls who like salt and vinegar = 23 So, boys who like salt and vinegar = 39 - 23 = 16 6. **Step 3: Find boys who like ready salted.** Total boys = 42 Boys who like cheese and onion = 17 Boys who like salt and vinegar = 16 So, boys who like ready salted = 42 - 17 - 16 = 9 7. **Step 4: Find total students who like ready salted.** Girls who like ready salted = 15 Boys who like ready salted = 9 Total ready salted likers = 15 + 9 = 24 **Final answer:** $$\boxed{24}$$ students like ready salted best.