We apply the Pythagorean theorem twice and obtain:
12 ^ 2 = x ^ 2 + (15-d) ^ 2
9 ^ 2 = x ^ 2 + d ^ 2
We observe that it is a system of two equations with two unknowns whose solutions are:
(x, d) = (-36/5, 27/5)
(x, d) = (36/5, 27/5)
We ignore the negative solution, therefore, the solution is:
(x, d) = (36/5, 27/5)
Answer:
The length of the new fence is:
x = 36/5 meters