Explain for and points thank you

Hi i’m not sure how to do question 20 if u could explain how to do it that’d b great

Solve for the equation. 4x - 13 = 2x + 9

Asix-sided die of unknown bias is rolled 20 times, and the number 3 comes up 6 times. in the next three rounds (the die is rolled 20 times in each round), the number 3 comes up 6 times, 5 times, and 7 times. the experimental probability of rolling a 3 is 10 %, which is approximately % more than its theoretical probability. (round off your answers to the nearest integer.)