I haven't taken the HESI, but I took both the NET and the TEAS V. I didn't purchase the TEAS V study guide but did use the Kaplan Nursing Entrance Test book and the McGraw-Hill book.
The math sections on both the NET and the TEAS V were very similar. So similar, in fact, that I scored a 93 in math on both exams! The major difference was that the TEAS does not permit you to use a calculator.
Here is a list of topics that appeared on my TEAS test:
-adding, subtracting, multiplying, dividing
-simplifying algebraic equations
-finding the value of x
-finding the area/perimeter(or circumferece) of a:
-pythagorean theorum to figure out one side of a triangle
-using the FOIL method
-basic every day math like balancing a check book
-metric conversions (I'm not sure if this was in the math or science section, but it did appear on my exam!)
Like I said, I'm not familiar with the Math on the Hesi, but aside from the roman numerals and maybe the metric conversions, the TEAS Math section was pretty basic math concepts.
I'm sure you'll do equally well on the TEAS math portion as you did on the HESI!