CAIE IGCSE Mathematics Extended E2.5.6 Solve Quadratic Equations Topic Practice

Martha walks a distance of 10 km at a speed of $x \mathrm{~km} / \mathrm{h}$.
She then runs a distance of 5 km at a speed of (x+4) km / h.
The total time taken for the whole journey is 3.5 hours.

Solve $7 x^{2}-2 x-80=0$, giving your answers correct to 2 decimal places.

You must show all your working.

or x=