Pattern 3, -6, 12, 4, 20, ?

On a string instrument, the length of a string varies inversely as the frequency of its vibrations. an 11-inch string has a frequency of 400 cylces per second. find the frequency of a 10-icnch string.

If olu is twice as old as funmi if the sum of their ages is 60 how old is olu

For what values of the variable x is the expression square root of 7x+14+ square root of 7-x a real number?