Cost A = 600+50y
Cost B = 1200+40y
the variables are the years that pass and the cost over time
Step-by-step explanation:

d. you already answered it. why do you need help? I'm confused. Is this a trick?
There are 60 seconds in a minute.
There are 60 minutes in an hour.
This means that there'd be 600 minutes in 10 hours.
And if there are 60 seconds in a minute, there are 600 x 60 seconds in 600 minutes.
600 x 60 = 600 x 10 x 6 = 6000 x 6 = 36000
So we know that there are 36000 seconds in 10 hours.
The answer is x=34 degrees.