yippee! so I am of some use after-allhaha, observant not so much. But I have been pranked many times so I kind of take most questions as a trick question. Btw, at first I mistook, multiplication sign in the last line as an addition sign, since before it, were all addition equations, so my first answer was (10+5+4), but then I scrolled down and saw your answer. So corrected my mistake.