Answer:
Step-by-step explanation:
For the random variable 
we define the possible values for this variable on this case ![[1,2,3,4,5]](https://tex.z-dn.net/?f=%20%5B1%2C2%2C3%2C4%2C5%5D)
. We know that we have 2 defective transistors so then we have 5C2 (where C means combinatory) ways to select or permute the transistors in order to detect the first defective:
We want the first detective transistor on the ath place, so then the first a-1 places are non defective transistors, so then we can define the probability for the random variable 
like this:
For the distribution of 
we need to take in count that we are finding a conditional distribution. given 
, for this case we see that ![N_2 \in [1,2,...,5-a]](https://tex.z-dn.net/?f=%20N_2%20%5Cin%20%5B1%2C2%2C...%2C5-a%5D)
, so then exist 
ways to reorder the remaining transistors. And if we want b additional steps to obtain a second defective transistor we have the following probability defined:
And if we want to find the joint probability we just need to do this:
And if we multiply the probabilities founded we got:
I'm sorry, but what digit is underlined?
X + (7 - 3i) + (5 + 9i) + 13i = 10 - 5i
Subtract 13i from both sides
x + (7 -3i) + (5 + 9i) = 10 - 18i
Subtract (5 + 9i). MAKE SURE YOU SUBTRACT 9i TOO. In other words, distribute the negative and subtract 5 and 9i at the same time.
x + (7 - 3i) = 5 - 27i
Do the same with (7 - 3i). You'll be adding 3i since -(-3i) = 3i.
x = -2 - 24i
