Just need help with 8,9,10

Savannah is painting a striped background for a mural on a wall that is 1515 yards long. she wants a total of 9696 stripes that are all the same width. which calculation should savannah use to decide how wide to make each stripe?

Two times a number plus three times another number equals 4. three times the first number plus four times the other number is 7. find the numbers

Abacteria population is tripling every hour. by what factor does the population change in 1/2 hour? select all that apply