Answer:
Katrina will have to pay $21.02 this month.
Explanation:
The cost per text message = $0.19
Last month credit = $9.50
The number of text messages sent this month = 158
So, the total cost of 158 texts = 158 x cost per text
= 158 x $0.19 = $ 30.52
So, her total bill = The amount spent on texts - The credit amount
= $ 30.52 - $9.50 = $21.02
So, Katrina will have to pay $21.02 this month.