Subtracting Percents / Fractions

I feel so embarrassed... use to do geom/trig on the fly now I can't do simple 5th grade arithmetic. Trying to figure out:

$\displaystyle 8\frac{1}{4}$ % - $\displaystyle 5\frac{2}{5}$%

Into:

$\displaystyle 8\frac{5}{20}$ % - $\displaystyle 5\frac{8}{20}$%

Into (where does the 25 come from? I see 1 was taken away from the 8, please explain)

$\displaystyle 7\frac{25}{20}$ % - $\displaystyle 5\frac{8}{20}$% = $\displaystyle 2\frac{17}{20}$

Converting to decimal it's:

0.0825 -0.0540 = 0.0285 or $\displaystyle =\frac{285}{10,000}$ simplified... I gave up.