Roslan had a total of $50 in 10-cent coins,20-cent coins and 50-cent coins. The value of his 10-cent coins was 30% of the total value of all his coins. The value of his 20-cent coins was 28% of the total value of all his coins. What was the value of his 50-cent coins?

What's the difference between: x≥0 and nonnegative integer. ?

What is the approximate difference in tenths between √12 and √15?

Sanya noticed that the temperature was falling at a steady rate of 1.4 degrees every hour from the time that she first checked her outdoor thermometer. by 6 a.m., the temperature had fallen 21 degrees. which expression can you use to find how many hours earlier she had first checked the thermometer?