Answer
$v = 7.2~m/s$
Work Step by Step
We can find the components of the boat's velocity relative to the ground:
$v_x = (8.0~m/s)~sin~30^{\circ}-2.0~m/s = 2.0~m/s~(west)$
$v_y = (8.0~m/s)~cos~30^{\circ} = 6.93~m/s~(north)$
We can find the magnitude of the boat's velocity relative to the ground:
$v = \sqrt{(2.0~m/s)^2+(6.93~m/s)^2}$
$v = 7.2~m/s$
