ANSWER:
283.9°
Explanation:
We must calculate the components of each vector, add the corresponding components to obtain the components of the resulting vector, like this:
![\begin{gathered} V_1=7\text{ mph, 25}\degree\rightarrow \\ \\ V_2=100\text{ mph, 280}\degree\text{ or 10\degree \lparen280\degree - 270\degree\rparen} \\ \\ \text{ x-axis components} \\ \\ V_(1x)=7\cdot\cos25\degree=6.34 \\ \\ V_2x=100\cdot\sin10\degree=17.36 \\ \\ \text{y-axis components} \\ \\ V_(1y)=7\cdot\sin25\degree=2.96 \\ \\ V_(2y)=100\cdot\cos10\degree=98.48 \\ \\ \text{ We calculate the components of the resulting vector taking into account the quadrant of the vectors \lparen for the signs\rparen:} \\ \\ V_x=6.34+17.36=23.7 \\ \\ V_y=2.96-98.48=-95.52 \end{gathered}]()
Knowing the components of the resulting vector, calculate the angle, as follows:

The angle of the resulting vector is 283.9°