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2014-02-25T15:06:36+01:00
(1/4 - 1/5) x (7 + 37/9)
= (1 x 5 / 4 x 5 - 1 x 4 / 5 x 4) x (7 x 9 / 1 x 9 + 37/9)
= (5/20 - 4/20) x (63/9 + 37/9)
= 1/20 x 100/9
= 1 x 100/ 20 x 9
= 100/180
= 20 x 5 / 20 x 9
= 5/9