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 sport balls. So we need to divide the number at the end of the equation by 3 to find the value of the first sport ball. The second line include always one of the first sport balls and another two same sport balls. So we subtract the value of the first sport ball from the number at the end of the equation and then divide the result by 2. Now we have the value of the second sport ball. The third line include one sport ball from the second line and again two new sport balls, but in different order. Then again we subtract the the value of the second sport ball and devide the result by 2. When we have the values of all 3 sport balls, the last fourth line is to add them to one another by simple addition and find the missing number. This app include the following sport equipment: Football, Basketball, Volleyball, Rugby, Bowling, Curling, Tennis, Baseball and Golf.