take the .5 of the 17.5 and convert it to a fractin.
we know .5 is equal to 50% or 1/2
now we have a mixed number [tex]17 \frac{1}{2} [/tex]
in order to convert it into an improper fraction you need to multiply the whole number by the denominator and then add the numerator all while keeping the denominator constant.
[tex]W \frac{N}{D} = \frac{(W*D)+N}{D} [/tex]
so [tex]17 \frac{1}{2}= \frac{(17*2)+1}{2}= \frac{35}{2} [/tex]