it cost Josiah $9.75 to send 65 text messages. How many text messages did he send if he spent $28.20

Let's call the number of text messages Josiah sent "x".

The cost per text message can be calculated as $9.75 / 65 text messages = $0.15 per text message.
We can set up the following equation:
$0.15 per text message * x text messages = $28.20 spent
0.15x = 28.20
Dividing both sides by 0.15, we get:
x = 28.20 / 0.15
x = 188
Therefore, Josiah sent 188 text messages.