20-10=10 therefore X=10
10+10=20
If it is area your looking for.
Area = product of diagonal lengths divided by 2
Area = 12* 16 /2
=192/2 = 96.
IF it is the side length of the rhombus:
apply Pythagoras theorem since the diagonals always meet at 90°.
L =√(12² + 16²)
L= √400 = 20
Answer:

Step-by-step explanation:

The answer is 12x+4 and 2(6x+2)
Hope it helps.