Answer:
3.2 ft
Explanation:
The initial distance from the base of the ladder to the wall is:
![20^2=16^2+d^2\\d=12\ ft](https://img.qammunity.org/2021/formulas/mathematics/high-school/afw96ylukj00zbxanf625oc5cm88060s7e.png)
After moving the ladder, the distance from the base to the wall is 12 - 2x while the height of the ladder is 16 + x. The distance x is given by:
![20^2 = (12-2x)^2+(16+x)^2\\400 = 144-48x+4x^2+256+32x+x^2\\5x^2-16x=0\\5x=16\\x=3.2\ ft](https://img.qammunity.org/2021/formulas/mathematics/high-school/fc1osm7eg7ze9km1rzz76b5u9h5p1seh8s.png)
Therefore, the top of the ladder is 3.2 ft higher now.