「5 Головоломок для детей, Которые не решить взрослым 〜 5 ＋ 5 ＋ 5 ＝ 55」 http://www.youtube.com/watch?v=UH4YsIGMZh4
〈 A trial supposition 〉
We should pay attention to what another 5 in the right side means.
Possibly, it may mean the number of bars found out in the left side.
Namely, 「5 ＋ 5 (＝ 10)」is calculated as usual, furthermore 0 is ignored, two crosses are composed of four bars, therefore, five bars are found out in the left side.
Simply, 5 × 100 ＋ 5 × 11 ＝ 555.
The following is a somewhat strange ( or irregular ) interpretation.
In the case, it's interpreted that 5 is composed of five bars.
And, plural 5s are pasted together so as to fill a gap with an other bar.
Surely, an independent cross ( composed of bars ) can be found out in such a pattern in each side.
