Question 1133239
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It is easy.


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From the condition (from the given data), you can restore the placement of the girls and the boys in the row, from left to right. 


It is as follows:


G1  G2  G3  B1  G4  G5  G6  B2  G7  G8  G9   G10   G11  G12  G13  G14  G15  B3   G16  G17  G18   B4  G19  G20  



Then the number of boys counted by each girl in front of she, is as follows:

G1  G2  G3      G4  G5  G6      G7  G8   G9   G10  G11  G12  G13  G14  G15       G16  G17  G18       G19  G20
4   4   4       3   3   3       2   2    2    2    2    2    2    2    2         1    1    1         0    0


So, the sum you are looking for is  4*3 + 3*3 + 2*9 + 1*3 + 0*2 = 42.


Now, having this solution before your eyes, it is not difficult to re-tell it in the compact form, by writing 
and justifying the last summation immediately, omitting all details that preceed.
</pre>

Solved, answered, explained and completed.