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 planets from the Solar System. So we need to divide the number at the end of the equation by 3 to find the value of the first planet. The second line include always one of the first planets and another two same planets. So we subtract the value of the first planet from the number at the end of the equation and then divide the result by 2. Now we have the value of the second planet. The third line include one planet from the second line and again two new planets, but in different order. Then again we subtract the the value of the second planet and devide the result by 2. When we have the values of all 3 planets, the last fourth line is to add them to one another by simple addition and find the missing number. This app include the following planets: Jupiter, Mars, Earth, Saturn, Uranus, Venus, Mercury, Neptune and Pluto.