Rail Chaos

WAS supposed to be playing in the Battersea Club Championship last night, but an "incident" meant I did not make our Battersea Labour Club venue in time.
I reached Waterloo, intending to catch a train to Clapham Junction, only to find there were numerous cancelations and delays.
That should not have been a problem as I had left plenty of time, but the train I was directed to catch got away late and so did not stop at Clapham Junction but went straight through to Surbiton.
By the time I caught a return train and reached the club, my opponent had been repaired and there was no one for me to play.
One consolation - the serial number of the South Western Railway carriage I rode in from Surbiton made for an interesting 'Tube Puzzle': 77713.
As usual, each number should be used once, and once only, and must be added, subtracted, multiplied or divided to make a balanced equation.
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My solution: 7 + 7  =  7 x ( 3 - 1)