Answer:
To Find => The value of x. in the equation below
=>

Step-by-step explanation:
We will cross Multiply the digits
=>20 \div 22 = x \div 20
=>We'll cross Multiply
=>

<em><u>Hence,</u></em><em><u> </u></em><em><u>1</u></em><em><u>0</u></em><em><u> </u></em><em><u>is </u></em><em><u>the</u></em><em><u> </u></em><em><u>required</u></em><em><u> </u></em><em><u>answer</u></em>
We are given an equation:

This is an equation of a circle. General form of a circle equation is:

Where:
a = x coordinate of a center
b = y coordinate of a center
r = radius of a circle
Motion detector can detect person anywhere within a boundary. The greatest distance at which detector can detect is at the edge of a circle. That distance, between detector and edge of circle, is equal to radius.
From the equation we have:

The greatest distance at which person can be detected is 4ft.