The sum of 3, 5, and a number is 15. why is the value of that number?

If f(x)= sqrt4x+9+2, which inequality can be used to find the domain of f(x)?

You can ride your bike around your block 6 times and the whole neighborhood 5 times in 16 minutes. you can ride your bike around your block 3 times and the whole neighborhood 10 times in 23 minutes. how long does it take you to ride around the neighborhood?

Find two numbers if their sum is 91 and the ratio is 6: 7?