If you're looking for the value of z, then the answer should be -5.
The correct answer is B.30 inches
The probability of rolling an even number on the first dice is 1/2(3/6)
The probability of rolling an even number on the first dice is also 1/2 (3/6)
So the probability of getting two even numbers on both dice is 1/2*1/2=1/4