Ехал на велосипеде 3 часа, со скоростью 12 км/ час. С какой скоростью он должен был ехать , чтобы преодолеть это расстояние за 2 часа

Помогите решить уравнение.

2х в 4 степени - 17 х во 2 степени - 9 =0 
 

Put the verbs in brackets into the past simple or the past continuous.

1.A: I...(call) you all afternoon yesterday but you weren`t home. 

   B: I..(stydy) in the library, with some kids from my class.

2.A: What..(Patrick/do) when Sam told him the truth?

   B: He..(start) shouting at him!

3.A: As I..(look) out the window, I..(see) a car crash into a tree.

   B: ..(you/call) the police?

4.A: Why..(you/take) the busto work this morning?

  B: Because as I...(drive) to the office, me car..(break) down.

5.A:..(the girls/help) you with the housework yesterday?

  B: Oh, yes! While Anna..(vacuum) the carpets, Alice..(clean) the windows.

6 A:..(you/know) that our dads..(go) to the same school when they were young?

  B: Really? I...(have) no idea!