Answer
4
Work Step by Step
We know:
$$ x(x+5) = 36 \\ x^2+5x-36 = 0$$
Since the coefficient of the squared term is one, we know that the expression must factor to:
$$ (x\pm a)(x\pm b)$$
Here, we see that a and b must multiply to get $-36$ and add to get $5$. Thus, we find that the solution is:
$$(x+9)(x-4)$$
Thus, setting each factor equal to zero, we find that the solutions are:
$$ x=-9,4$$
x must be positive, so:
$$x=4$$
