Well, the first ballon appears to be halfway to the second (the second being 300 meters from the ground) so the first, being at approximately 150 meters, both away from the ground and the balloon, would have to travel a further 150 meters.
To find this you would do 800 + 15x where x is the amount of years.
For 9 years it would be 800 + 15(9) which is 800 + 135.
At the end of 9 years, the apartment's rent would be $935. I hope that's utilities included because... yikes...
A fraction is numerator over denominator, most of the time whole numbers
