Precalculus (6th Edition) Blitzer

The average velocity of the plane is $\text{725 }{\text{km}}/{\text{h}}\;$ and the average velocity of the wind is $\text{75 }{\text{km}}/{\text{h}}\;$.
Consider the average velocity of the plane to be $x$ and the average velocity of the wind to be $y$. The average velocity of the plane in the direction of the wind is $x+y$ and the average velocity against the wind is $x-y$. A plane takes $2$ hours to travel $1600\text{ km}$ in the direction of wind and it takes $3$ hours to travel $1950\text{ km}$ against the direction of wind. The equations from the table give: \begin{align} & 2\left( x+y \right)=1600 \\ & x+y=800 \end{align} …… (1) And \begin{align} & 3\left( x-y \right)=1960 \\ & x-y=650 \end{align} …… (2) Add equation (1) and equation (2). \begin{align} & \underline{\begin{align} & x+y=800 \\ & x-y=650 \end{align}} \\ & 2x\text{ }=1450 \\ & \text{ }x\text{ }=725 \\ \end{align} Substitute $x=725$ in equation (1). \begin{align} & x+y=800 \\ & 725+y=800 \\ & y=800-725 \\ & y=75 \end{align} Therefore, the average velocity of the plane is $\text{725 }{\text{km}}/{\text{h}}\;$ and the average velocity of the wind is $\text{75 }{\text{km}}/{\text{h}}\;$.