Answer
$t=6$ and $t=10$
Work Step by Step
The Graph's axis are seconds (x) and meters/secons (y) so the area underneath the graph corresponds with: $$\frac{m}{s} \times s = m$$
The area underneath the curve adds to 35 at time $t=6$ with a cumulative total, and later at time $t=10$ because negative area brings the total distance back down to 35 after the particle's velocity becomes negative.
