Ok I found my mistake. I averaged the total speed by mistake and used it in place of the acceleration.
here is the correct equation set up.
2(3) +1/2(4)(3)^2=24
I must think too far into the problem, and got to slow down.
I am currently doing the self-test in Ch1 of Basic Physics: A Self-Teaching guide, by Karl F. Kuhn. I am trying to teach myself the basics of physics so I can be ready for March's session of physics class. I had a go at it for 2 days and realized i was going to fail unless I did something to be...