IMC 2007 — Keystage 3 (IWYMIC) — individual Question 10

Use each digit $2,3,4,5,6,7,8,9$ once in the eight boxes of $$\frac1{\Box\times\Box}+\frac\Box{\Box\times\Box}+\frac\Box{\Box\times\Box}=1.$$ What is the largest of the three fractions?