This confuses me s much i don't get it

So the perimeter of the rectangle would be (after adding everything) 8x + 2 
The perimeter of the square would be (again after adding everything) 12x

So if the perimeters are the same, then 8x + 2 = 12x

And then the way I would do this (no not really but i'm too lazy to explain) because I'm lazy is subtract 8x from both, until you get 2 = 4x.

Divide each side by 4, and you'll get 1/2 = x

And then since the perimeters are the same, we can take the simplest one, of the square, or 12x, and replace 1/2 with x, and you'll get 12 * 1/2, or 6.

Actually you wanted the dimensions. oops.

The rectangle, x is straightforward, it's 1/2. The other side is 2.5, because 3 * 1/2 + 1 = 2.5.

The square is literally just 3 * 1/2 * 4. Or 6.