How do you calculate with real world measurements

Solve the inequality: - 3 (-3x - 4) < 66

The sum of three consecutive even numbers is 42. What is the smallest of these numbers. Explain

A group of researchers wanted to monitor the trout population, so they marked 340 trout with tags. Later, they captured 600 trout and found that 30 of them had tags.

A company that produces thumb drives has determined that its maximum profit occurs when it sells 5,000 units per month.

You lose your electronic tag that you use to pays tolls on the highway in your city. It costs you $24 to replace the tag. The costs of one toll when you don't use tag is $3. The cost of the same toll when you do use the tag is $1.50.

A newspaper reporter wants to know how popular the hobby of bird watching is in the city. He asked people at the local bird refuge if they watched birds as a hobby. Which of the following best explains whether the reporters data is valid or not?

I am very confused on how to figure out if y = 3/4x is proportional?

Alison wants to buy a mountain bike for $339.12. If she saves $28.26 each month, in how many months will she be able to buy the bike?

At 12 o'clock the temperature was 7°C. The temperature decreased by - 20°C. What is the new temperature?

Ashleys rentals charges $27.50 per hour to rent a surfboard and a wetsuit. Darlas surf shop charges $23.25 per hour to rent a surfboard plus $17 extra for a wetsuit.