First, lets write the equation: CuBr--> Cu+2 + Br-
then, write the Ksp expression: Ksp= [Cu+2] [Br-]= 6.3 x 10-9
We let x be the concentration of Ksp that dissolved. Ksp= (x) (x)= 6.3 x 10-9.
Now we solve for x
X^2= 6.3x10-9
x= square root(6.3x10-9)
x= 7.94x10-5