Since this is a square, all of the sides are equal to each other.
That means we can take the two sides with an [tex]x[/tex] term in them (the bottom and the right ones) and set up an equation that has them equal to each other and then solve for [tex]x[/tex]:
[tex]3x = 5x - 4[/tex]
Let's move the terms with an [tex]x[/tex] to the left side of the equation:
[tex]3x - 5x = -4[/tex]
[tex]-2x = -4[/tex]
Now we can divide both sides by -2 to get [tex]x[/tex] by itself.
[tex]-2x = -4[/tex]
[tex]x = 2[/tex]
We can plug this into either of those sides to get the length of the sides of the square:
[tex]3x[/tex]
[tex]3(2)[/tex]
[tex]6[/tex]
Now that we know each side of the square is of length 6, we can take one of the remaining sides and set it equal to 6 and solve for [tex]y[/tex]:
[tex]5y + 1 = 6[/tex]
[tex]5y = 6 - 1[/tex]
[tex]5y = 5[/tex]
[tex]y = 1[/tex]