Let the width of the river be D

Now, considering their speeds on y-axis i.e. perpendicular to the motion of stream

$v_{Ay} = v_Asin60°$

$v_{By} = v_B$

$v_{C} = v_Csin60°$

Now, as they reach the opposite end at the same time

$\frac{d}{v_{Ay}} = \frac{d}{v_{By}} = \frac{d}{v_{Cy}}$

$\frac{1}{v_{Ay}} = \frac{1}{v_{By}} = \frac{1}{v_{Cy}}$

$v_{Ay} = v_{By} = v_{Cy}$

$v_{A}sin60° = v_{B} = v_{C}sin60°$

Now, as $sin60° \lt 1$ , so the order is $\color{#3D99F6}{\boxed{v_{B} \lt v_A = v_C}}$

The only thing that matters for the boats to reach the other side of the river is their velocity(direct speed) towards the other side. Boat A goes in a straight line(90 degrees) so it has the shortest distance to the other side. Boats B & C go in the same tilted angle ,the only difference is that one is tilted to the right and the other is tilted to the left( |90-X| ), so they require to go through a longer distance than boat A. All boats reach the end at the same time which means that boats B & C are faster than boat A (distance/time=speed) and since boats B & C went through the same distance they have the same speed. In short : velocity of boat A < velocity of boat B = velocity of boat C