To find the speed of the boats we will divide the distance by time.
From the graph we finde the boats' speeds as ;
\(Boat\quad 1\quad =\quad \frac { 35 }{ 5 } =\quad 7\quad km/h\\ \\ Boat\quad 2\quad =\quad \frac { 35 }{ 7 } =\quad 5\quad km/h\)
And for the speed of the third boat, we will also divide the distance by time.
\(Boat\quad 3\quad =\quad \frac { 32 }{ 4 } =\quad 8\quad km/h\)
As you can see the speed of boat 3 (8 km/h) is more than boat 1 (7 km/h) and boat 2 (5 km/h).
Thus the third boat is faster than both of them.
The answer is B.
You can see the speed of boat 1 and 2 in the picture.
