URGENT!!! which is a true statement about triangle ABC?

Answer:
1st option
Step-by-step explanation:
In right triangle BCD
cosC = [tex]\frac{adjacent}{hypotenuse}[/tex] = [tex]\frac{b-x}{a}[/tex] ( multiply both sides by a )
b - x = acosC ( subtract b from both sides )
- x = acosC - b ( multiply through by - 1 )
x = b - acosC