We know that each length/width needs to be equal. The width is 10, so we need to find something of y to equal 10. We have the equation 2y + 4 = 10. We need to isolate y. We can do that by subtracting 4 from both sides. This gives us 2y = 6. Next, we need to divide both sides by 2. This gives us y = 3.
The value of y is 3.
