What is the missing expression?

x^8 + 3x^5 =

To prove that def ~ gfh by the sss similarity theorem using the information provided in the diagram, it would be enough additional information to know that

The longer leg of a 30° 60° 90° triangle is 16 times square root of three how long is a shorter leg

For what values of the variable x is the expression square root of 7x+14+ square root of 7-x a real number?