Thanks!
For X~N, shouldn’t the variance be 5^2 instead of 5 and Y~N as 4^2 instead of 4?

notation for normal distribution is N(mean, var).

if the question gives std dev as 5,
then var is 5^2 and we write the distribution as
X~N(8, 5^2)

however, for this question, it is given that var is 5, so we write the distribution as X~N(8,5)

note that when you use the normalcdf function in the TI-84 GC, you need to enter std dev instead of var.
so for W~N(19,9), you need to enter as mean = 19 and std dev = sqrt(9) = 3.

a bit messy, but its the way the GC is programmed.

I see, thx for explaining