how to do this??

11/15=(1/a+(b/c+(d/e+f)))

find a,b,c,d,e, and f??

one step at a time...

11/15=(1/a+(b/c+(d/e+f)))
11 = 15(1/a+(b/c+(d/e+f)))
11 = 15/a + 15(b/c+(d/e+f))
15/a = 11 - 15(b/c+(d/e+f))
a = 15/(11 - 15(b/c+(d/e+f)))

Now for b:

11 = 15/a + 15(b/c+(d/e+f))
15(b/c+(d/e+f)) = 11 - 15/a
(b/c+(d/e+f)) = 11/15 - 1/a
b/c = 11/15 - 1/a - (d/e+f))
b = c(11/15 - 1/a - (d/e+f)))

now you can find c,d,e in similar wise. Kind of useless exercise. After a and b, you're not really learning anything by grinding through c,d,e.