Hi everyone. I have this problem. Given three random variables X, Y, Z with joint pdf (probability density function)
f(x,y,z)=\exp(-(x+y+z)) if x>0, y>0, z>0; 0 elsewhere
find the pdf of U (f_U), where U is the random variable given by U=(X+Y+Z)/3.
Now I know how to find the joint pdf...