Find the maximum value of c=x+3y

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.)

Dylan is evaluation the expression 13+19+7+10 at one step in his work, dylan rewrites the equation as 13+7+19+10 which property of addition must dylan have used when he evaluated the expression?

Find the solution of this system of equations -7x+y=-20 9x-3y=36