4 and 9
Because 4+4+9+9=26
And 4x9=36
You can use trial and error or substitution.
Equation 1. 2x + 2y = 26
Equation 1. x = 13 - y
Equation 2. xy = 36
Equation 2. x = 36/y
Equation 1 = Equation 2 to equal equation 3. Then move all the terms to one side and factorise to get your answer.
Equation 3. 13 - y = 36/y
Equation 3. y squared - 13y + 36 = 0
Equation 3. (y - 4)(y - 9)
y = 4 or 9
Therefore the dimensions are 4 and 9