ok , i'M not sure
here is my answer
0.7(19)+0.3(17) , i know it's simple
X is normal with mean 9 and standard deviation 19
Y is normal with mean 11 and standard deviation 17
edit: the correlation between them is 0.6
What is the standard deviation of 0.7X + 0.3Y? I think I may know, but I want to be sure I'm getting it right.