where a, b and c are natural numbers and 0 < a < b < c.
Prove that a < 3 and also that b < 4 and hence that there is only one set
of values which satisfy this equation.
Find the six sets of values which satisfy the equation
1
a
+
1
b
+
1
c
+
1
d
= 1
where a, b, c and d are natural numbers and 0 < a < b < c < d.