Request for help - CHIJ St Nicholas 2009 Prelim Paper 2 Q17

Hello everyone, I received an email from a reader seeking some help. Below is the email reproduced unedited. Please feel free to help.

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Hi,
I am a regular reader of your blog "road-to-psle". I have 1 question from CHIJ St Nicholas 2009 Prelim Paper 2 Q17 that I cannot solve. I have asked many people including tutors and teachers but they also cannot solve. Can you please help me? The question:

At Carpark P. the number of lorries to that of vans was in the ralio 3: 7.
At Carpark Q, the number of lorries to that of vans was in the ratio 8: 9.
When 40% more lorries from an industrial park entered Carpark P and
20% of the vans at Carpark Q moved to Carpark P. there were 76 fewer
Iorries at Carpark P than at Carpark Q. How many vehicles were there
altogether at the two carparks finally? Ans:564

Thanks
John

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Please post solutions here.

http://www.atfreeforum.com/excel/viewtopic.php?p=5&mforum=excel#5