Answer
$25s$
Work Step by Step
First of all, determine your velocity relative to the walkway, that is:
$\vec{v_{yw}}=\frac{\Delta x}{\Delta t}\hat x=(1.25\frac{m}{s})\hat x$
Now find your velocity relative to the ground:
$\vec{v_{yg}}=\vec{v_{yw}}+\vec{v_{wg}}$
Where $\vec{v_{yg}},\vec{v_{yw}},\vec{v_{wg}}$ represent your velocity relative to the ground, relative to the walkway, and walkway relative to ground respectively.
We plug in the known values to obtain:
$\vec{yg}=(1.25\frac{m}{s})\hat x+(2.2\frac{m}{s})\hat x=(3.4\frac{m}{s})\hat x$
Now we can find the required time
$t=\frac{\Delta x}{v_{yg}}$
$\implies t=\frac{85}{3.45}$
$t=25s$
