We know it is 16:9. So we know that 16 is the length and 9 is the height. Ben gave us height, which is 4. Now, we must find the length. To do this, we do this:

16/9 * x/4

If you look at the equation, you will see that the height is 9 on the left, and 4 on the right. We know that the length is supposed to be 16, but we donโt know what it should be if the HEIGHT is to be 4. And so, we place an โxโ.

By cross multiplying, we end up with x = 4(16)/9

Which gives us 7.11

Hope that helps