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 country flags. So we need to divide the number at the end of the equation by 3 to find the value of the first flag. The second line include always one of the first country flags and another two same country flags. So we subtract the value of the first flag from the number at the end of the equation and then divide the result by 2. Now we have the value of the second flag. The third line include one flag from the second line and again two new country flags, but in different order. Then again we subtract the the value of the second flag and devide the result by 2. When we have the values of all 3 country flags, the last fourth line is to add them to one another by simple addition and find the missing number. This app include the following country flags: USA, UK, EU, Japan, China, Russia, Bulgaria, Spain and France.