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No...
you have miscalculated it...
try again

I don't get it then...
One apple is worth 7
One grape is worth 1
One banana is worth 2
Am i right?

Or is it that there are supposed to be 12 grapes so that the answer would be 21?

I am sorry... I was miscalculating the answer... you were right 20 is the right answer
Apple = 7, grapes = 11 and banana = 2

Nice, thank you :D