Can someone me with this problem 30

Solve: 3x+y=6 4x-2y=18 show all work !

Atown has a population of 12000 and grows at 3.5% every year. what will be the population after 7 years, to the nearest whole number?

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.)