The answer is true, but Im not 100%
In ΔAOD (AD) =(AO)
2+(OD)
2 =36+64 AD
2 =100
AD= 100
=10cm
Rhombus has all sides equal
AB = AD = BC = CD = 10 cm
Hello!
Equation: 
To solve, we will need to take the roots:

Answer:
or 
The answer to your question is 7