Hi there!
The general formula to find the perimeter of a rectangle is :
P = (Length × 2) + (Width × 2)
Let's say the width of the rectangle is "x".
The lenght of the rectangle is equal to 2x + 4.2
Replace everything you know in the formula :
42.6 = ((2x + 4.2) × 2) + ((x) × 2)
Simplify everything :
2x × 2 = 4x
4.2 × 2 = 8.4
x × 2 = 2x
42.6 = 4x + 8.4 + 2x
42.6 = 6x + 8.4
Isolate "x":
42.6 = 6x + 8.4
Subtract 8.4 from each side of the equation
34.2 = 6x
Divide each side of the equation by 6
5.7 = x
5.7cm = the width of the rectangle
Since the lenght of the rectangle is equal to 2 times the width of the rectangle plus 4.2 :
Length = (2 × 5.7) + 4.2
Length = 15.6cm
42.6 = (2 × 15.6) + (2 × 5.7) ? → YES
There you go! I really hope this helped, if there's anything just let me know! :)
