Zachary S. answered 04/17/19
Mathematician/Developer w/ Experience Teaching Geom, Alg, Calc, More!
An arithmetic sequence is one where the difference between a term and the next one is a constant. I like to think of it as a step size: the distance from a1 to a2 or a5 to a6 is the same.
So to go from a1 to a6 we've taken 5 steps, and covered a distance of a6-a1=29-4 = 25.
As the steps are all the same size, our step size is 25/5 = 5.
So to find a32 we could just keep adding 5 over and over again, but note that this is 31 steps beyond a1. So
a32= a1+ 5*(31 steps) = 4 + 155 = 159.