Should i add, multiply, subtract, or divide n+16=9

What is the answer to this problem 7 * 5/6

Your food costs are $5,500. your total food sales are $11,000. what percent of your food sales do the food costs represent?

In priyas math class there are 10 boys and 15 girls. what is the ratio of boys to girls in priyas math class? express your answer as a decimal