Answer: $78 is the Madyson's final payment.
Step-by-step explanation:
Since we have given that
Amount from her father to purchase airplane tickets = $1200
On first week , she paid = $50
According to question it is mentioned that she is able to repay her father $2 more than the previous week, except in the last week.
So, we will apply "Arithmetic Progression"
a = $50
d = $2
So, we know the formula for "Sum of n terms "
Now, we will apply "Quadratic formula "
So, after 7th week its amount will be
so, Madyson's final payment will be
Hence, $78 is the Madyson's final payment.