Peter's phone had an initial credit balance of Ksh 20. He sent five text messages, each costing Ksh 2.
Using a number line, show how Peter's credit decreases with each message and determine his final credit balance.
Initial credit: Ksh 20
Cost per message: Ksh 2
Number of messages: 5
Total cost: 5 × Ksh 2 = Ksh 10
Final balance: Ksh 20 - Ksh 10 = Ksh 10