Based on the right-angles triangles shown above, the value of x is equal to 1 unit.
According to the geometric mean (leg) theorem, the length of the leg of a right-angled triangle is the geometric mean between its hypotenuse and the segment of the hypotenuse which is adjacent to that leg;
Hypotenuse/leg = leg/part
where;
hypotenuse = 9
leg = 3
part = x
By applying geometric mean (leg) theorem, the length of the part (x) can be calculated as follows;
AC/AB = AB/AD
9/3 = 3/x
9x = 9
x = 9/9
x = 1 unit.