What 1+1! I need help please. On my Test!

The sum of two numbers is 86, and their difference is 20. find the two numbers

Scores on a university exam are normally distributed with a mean of 78 and a standard deviation of 8. the professor teaching the class declares that a score of 70 or higher is required for a grade of at least “c.” using the 68-95-99.7 rule, what percentage of students failed to earn a grade of at least “c”?

If you have 12 feet of string and you cut it into equal length of 5 inches each how much string will be left