This problem has 2 solutions: 34 or 45. 

Method 1: The actual total of each line is added to the real total of the line after that. So: 1+4=5 (2+5) +5= 12 (3+6) +12=21 therefore the last equation must be: (5+8) + 21= 34.

Method 2: 45 - The key is that you multiply the first two numbers together and, afterwards, add the first number to the total (5*8=40, 40+5=45). Another way to get the same result (but is trickier) is to add 5 plus a multiple of 2 to the end total of each line, but the reason it gets trickier this way is that the 3rd line doesn't show up (they skip a line). This is probably the way they intended us to solve it. So, the first one, you add 5+2 (or 7) to 5 to get 12. The second, you add 5+4 (or 9) to 12 to get 21. The third one is skipped (so you would have added 5+6 (or 11) to 21 to get 32). The last line, you add 5+8 (or 13) to 32 to get 45.