b) If the probability of rolling two 5 's is eyual to three times the probability of obtaining a 5 followed by nota 5, find the value of $x$

Step 1 ：First, we need to find the probability of rolling two 5's. Since each roll is independent, the probability of getting a 5 on any given roll is \(\frac{1}{6}\), and the probability of not getting a 5 on any given roll is \(\frac{5}{6}\). So the probability of rolling two 5's is \(\left(\frac{1}{6}\right)^2\).

Step 2 ：Next, we need to find the probability of obtaining a 5 followed by not a 5. This is simply \(\frac{1}{6} \cdot \frac{5}{6}\).

Step 3 ：Now, we are given that the probability of rolling two 5's is equal to three times the probability of obtaining a 5 followed by not a 5. So we can set up the equation: \(\left(\frac{1}{6}\right)^2 = 3 \cdot \left(\frac{1}{6} \cdot \frac{5}{6}\right)\).

Step 4 ：Solve the equation: \(\frac{1}{36} = \frac{15}{36}\).

Step 5 ：Divide both sides by \(\frac{1}{36}\) to find the value of x: \(x = \frac{\frac{15}{36}}{\frac{1}{36}}\).

Step 6 ：Simplify the fraction: \(x = \boxed{15}\).