Examples is a+bi the conjugate is a-bi,if your adding the two conjugate its going to be 2a and if your subtracting the result is 2bi.And if multiplied it is seen as complex number which are a²+b²
2/7 is the probability that the first satellite sends a weak signal. That leaves 6, one of which sends a weak signal. So the probability that the second also sends a weak signal is 1/6. Combine these and we get 2/7×1/6=1/21.