I'm stuck on b.
please help me​

The area under the speed curve tells you how much distance the vehicle covers.

The distance for first 30 s corresponds to the area of a rectangle with height k m/s and length 30 s, or

(k m/s) (30 s) = 30k m

The distance for the last 20 s corresponds to the area of triangle with height k m/s and length 20 s, or

1/2 (k m/s) (20 s) = 10k m

If the total distance traveled was 1.7 km = 1700 m, then

30k + 10k = 1700

40k = 1700

k = 42.5

on friday there were 15 birds