Complete question :
There are 575 fireworks to be shot off in a firework display every minute 12 new fireworks are shot off display write a verbal model and algebraic expression to represent the number of fireworks left to be shot off after t minutes. 
Answer:
575 - 12t
Explanation:
Given the following :
Total number of fireworks = 575
Number of shots per minute = 12
To calculate the number of fireworks left to be shot off after t minutes, The total number of fireworks already shot after the same time interval t in minutes, is first obtained, this is equivalent to (12*t). The result is then subtracted from the total number of fireworks to be shof off. 
In algebraic terms 
[total number of fireworks on display - (number of shots per minute × t)] 
575 - 12t