To find answer,you first need to find the answer to 10*6. You need to multiply 6 and 10 together because 1 pizza is $10 and Timmy buys 6 pizzas every week so so far you've spent $60. Now the most amount of hair gel Timmy can buy is 10. Timmy can buy 10 hair gels because 1 hair gel is $4 and when you multiply 4 w/ 10 (10*4) you get $40. So now you add 60 and 40 together to get 100.
I hope this helps