Probability of Choosing Mathematics or Science

A school organizes a quiz competition where each student can choose to answer either Mathematics, Science, or English questions. The data from the last competition showed that:

• 20 students chose Mathematics
• 15 students chose Science
• 10 students chose both Mathematics and Science
• 5 students chose all three subjects
• There were no students who chose only English.

If a student is randomly selected from those who participated in the quiz, what is the probability that the student chose Mathematics or Science?