Which point is on the graph of f(x)=3 times 5^x

Which expression can be used to determine the slope of the line that passes through the points -6, three and one, -9

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.

∆red ≅ ∆ by rule will give brainiest if possible