Answer:
10cm
Explanation:
As you can see in the first image is a rhombus with its diagonals 12cm and 16cm
You can see that the diagonals divide the rhombus into four right triangles and that the hypotenuse of each triangle is one side of the rhombus.
In the second image I picked out one triangle from the rhombus and slashed the length of the diagonals of the rhombus in half to get the sides of the triangle.
Now all you have to do is use the Pythagorean theorem to find the hypotenuse of the triangle which will give you the length of side of rhombus
6² + 8² = hypotenuse²
36 + 64 = h²
100 = h²
h = √100
h = 10
All the side of the rhombus are equal so all the sides of the rhombus are 10cm