Answer:
200
Explanation:
You can use the equation 1300=4x+500
Starting bonus ($500) is like the y intercept so you would get that out of the way by subtracting 500 from both side
1300-500=800
500-500=0
Your equation is now:
800=4x
Now since the question is How many subscriptions did they sell and we know that each magazine is $4 all for have to do is divide both sides by 4 to get the answer.
800÷4=200
4x÷4=x
x=200