Dashed lines mean add, and solid lines mean multiply.

For example, two dashed lines point from ? and \large 3, so we add those numbers together to fill in the circle they point at.

What number must go in the yellow marked circle?

Correct Answer

We can work backwards starting from the \large 16 we know the circles that lead to it multiply to be \large 16, and one of the values is \large 2. Since \large 2 \times 8 = 16 the other value has to be \large 8.

Now we know the bottom portion is \large ? + 3 = 8 the question mark needs to be \large 5 for the addition problem to work.

Incidentally, this process is equivalent to solving for \large x in the equation \large 2(x+3) = 16. It's fairly natural in the charted form to work backwards from the \large 16, and this is exactly what needs to be done to solve when the equation is in algebraic form.