(plz answer) unicorn is writing an equation to represent the perimeter of a rectangle with the width equal to half the length. she knows that the perimeter is equal to 18 units and needs to find the length and width of the rectangle. which equations represent this relationship? check all that apply. 1.- x+ 1/2 x = 18 2. 2x + x = 18 3. 2(x) + 2(2x)= 1/2x =18 4. x+ 1/2 x + x + 1/2x= 18 5. 2 [ x + 1/2 x} =18