ok... let's say, the pieces are "a", "b", and "c".
"a" being the shortest and "c" being the longest
we know the longest is 38 more than the shortest, so
c = a + 38
and the third piece,
b,
is half the longest, or
c/2
we know the three pieces come from the 102in ribbon, thus
a + b + c = 102

solve for "a".
c = a + 38, and b = c/2