Think of an answer before reading the solution...
Four easy steps to solve this puzzle:
Now, here are the most common wrong answers that people think of:
Wrong! Notice that the operator between 5 and 1 is multiplication.
Wrong! Notice that there are three erasers in each bundle in the third line of the puzzle.
Wrong! Both the above mistakes.
Wrong! Note that multiplication goes first, then the addition. This is called precedence.