How do i do this? circled ones are the ones i need with

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.

Acar loses a quarter of its value every year. it is originally worth $35,000. to the nearest dollar,how much will the car be worth in 8 years?

Aline has a slope of negative 1/4 the past two points -5/4 and 1 what is the equation of the line