Please see the attached file.
The speed of waves on a certain string is 2 m/s. Another string has a mass per unit length that is 4 times as great as the first string and a tension that is 2 times as great. What is the speed of waves on the second string.
It shows how to calculate the speed of waves on the string given the tension. The solution is detailed and was rated '5/5' by the student who posted the question originally.