So now they gave 10 QR first and take 1 QR back so each of them gave 9 QR. 3x9 = 27 QR and 2 QR is at the waiter so

the total is 27+2= 29 QR
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bill was 25QR,  27QR is including the tip of the waiter and the 3 friends each have 1 QR with them so

27+3=30Tongue out