How do i solve this problem 6-y+5y-6y

Place the following steps in order to complete the square and solve the quadratic equation,

Mat bought a phone for $100. he has to pay $30 per mouth. if he has paid $640 in total, how many mouth has he had the phone?

Travis has decided to budget his spending money. he can spend no more than $143.15 every month. he has also decided to spend 5.2 times as much money on video games as he spends on the movies. what linear inequality describes this problem