Got caught up here... would greatly appreciate some help in working through these...

An object moves along so that it's location is -5x + 2x . Find velocity at following points: 1, 3, 5.

This is using derivatives and finding the velocities at the points. I've used what i know to find the slope of the tangent and secant line... unless I did my math wrong thats not how to find the answer. Any advise please?

Also, if someone can show me a method of solving a derivitive with a fraction, that'd be great.