Answer
$\approx7.22 \thinspace km$
Work Step by Step
On a velocity-time graph, the distance traveled can be found using the area under the curve. If we count the boxes under the curve between $t=0$ and $t=30s$, we see there are about 26 whole boxes. The size (area) of each box is:
$20\ km/h\times5\ seconds = 100 \frac{km\thinspace s}{hr}$.
There are 3600 seconds in an hour.
$\left(\approx 26\ boxes*100\frac{km\thinspace s}{hr}\right)\left(\frac{hr}{3600\thinspace s}\right)\approx0.722\thinspace km$
