Py +7 = 6y + qp
Solve the equation for y
To solve the equation for y we need to get y alone
Py +7 = 6y + qp
Subtract 6y from both sides
Py - 6y +7 = + qp
Subtract 7 from both sides
Py - 6y = + qp - 7
Now factor out y
(P - 6)y = qp - 7
Divide by P - 6 from both sides

Answer: 7 feet
Step-by-step explanation:
Since all 4 sides of a square are equal, you do 28 / 4 = 7 feet, which is the answer.