Computing probability using a density function

[Izumi]

X and Y are independent random variables with expected values 2 and 5. Determine the density function for Z=X+Y. Hence compute the probability P (Z>1)

 

[Romsek]

There isn't nearly enough information given to solve this problem. You are supposed to come up with a density function based only on the expected values? Neat trick if it were possible.

 

[Izumi]

There isn't nearly enough information given to solve this problem. You are supposed to come up with a density function based only on the expected values? Neat trick if it were possible.

Yeah coming up with the density function comes first then computing the probability

 

[Romsek]

you need more info... really you need to be told the density function