This is a question with lots of probabilities of a person bringing a pen, a pencil, and a highlighter and could bring any type of colour pen, pencil, or highlighter. The list above shows all the 24 possibilities. Although a tree diagram would have been more clearer, the list still shows it well.
This is a maths strategy that requires all of your times tables to be known. For example, 4 x 243. Place value is also needed so you split 243 into 200+40+3. Then you make 4 groups of 200+40+3 because you are multiplying by that number. 4 x 3= 12, so you cross out the 3 in your groups. 4 x 40 is 160, so cross out all the 40s. 4 x 200 is 800, so cross out the 200s. Add 12+160+800 together, and you get 972. 4 x 243= 972.