This is one 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 computer components. So we need to divide the number at the end of the equation by 3 to find the value of the first computer component. The second line include always one of the first computer components and another two same computer components. So we subtract the value of the first computer component from the number at the end of the equation and then divide the result by 2. Now we have the value of the second computer component. The third line include one computer component from the second line and again two new computer components, but in different order. Then again we subtract the the value of the second computer component and devide the result by 2. When we have the values of all 3 computer components, the last fourth line is to add them to one another by simple addition and find the missing number. This app include the following computer components: HDD, RAM, PSU, Mouse, Keyboard, Headphones, Monitor, Printer and Projector.