Let's assign the speed of Jerry in still air as <em>x </em> (in km/h)
Let's assign the speed of the wind as <em>y </em>(in km/h)
With the wind as Jerry’s back, he takes 10 minutes to get to the library. We can create the following equation. (<em>we are converting the minutes to hours by dividing by 60</em>);
2.5 / (x + y) = 10/60
10x + 10y = 150
x + y = 15
With the wind against Jerry, he takes 15 minutes from the library. We can create the following equation;
2.5 / (x-y) = 15/60
15x – 15y = 150
x – y = 10
We can now solve the simultaneous equation by subtraction;
