ANSWER:
a. 12.5%
b. 60 times
c. 16.67%
d. The theoretical is an ideal event, in reality there are many more factors that affect the probability of an event.
Explanation:
a. The experimental probability is the one obtained through the 360 attempts, therefore, the probability of rolling a 3 is 45 divided by 360. Just like this:

The experimental probability is 1/8
b.
Starting from the previous probability we can calculate the number of times that 3 would land if it is thrown 480 times (120 more times)

I would land a 3 total of 60 times
c.
The theoretical probability would be the number of times the 3 appears on a die (1) divided by the total number of faces on a die (6)

d.
The results of an experiment do not always agree with the theoretical results, but they become closer after a large number of attempts. This is because the theoretical probability is an ideal event, while the experimental probability has many more nuances to consider and is totally reality.