Because you need 100 feet of fencing to go all the way around, the circumference of the rectangle is 100.
Then, because this is a rectangle, both sides of the length are equal and both sides of the width are equal.
Therefore, we can represent the circumference with the following equation:
100=2(30)+2x, where x is the width.
Then we solve for x be rearranging the equation.
First simplify:
100=60+2x
Then subtract 60 from both sides
40=2x
Then divide both sides by 2
20=x
Therefore, the width of the garden is 20 feet.
