This is another example of combination system equation with overall 3 unknown values that have been very popular lately. To solve it we need simple math and logic skills. The first line usually consist of 3 same banknotes. So we need to divide the number at the end of the equation by 3 to find the value of the first banknote. The second line include always one of the first banknotes and another two same banknotes. So we subtract the value of the first banknote from the number at the end of the equation and then divide the result by 2. Now we have the value of the second banknote. The third line include one banknote from the second line and again two new banknotes, but in different order. Then again we subtract the the value of the second banknote and devide the result by 2. When we have the values of all 3 bills, the last fourth line is to add them to one another by simple addition and find the missing number. This app include the following banknotes: US Dollar, EU Euro, GB Pound, Japanese Yen, Chinese Yuan, India Rupee, Russian Ruble, Bulgarian Lev, Turkish Lira.