How would you solve this series of equations?

9 * 7 = ____ + 7 = ____

I think your answer may depend on how much math you’ve taken, and how recently. But let’s back up first.

Leslie and I teach Sunday School at our church.

…

You have now recovered from your shock, so we can continue. This is our first time teaching, and we rely heavily on materials created by Faith Alive Resources to help us figure out what to talk about every Sunday. We deviate from the script a little where it’s a little too ambitious or a little too simplistic, but for the most part the material is good for the age range we teach (4th/5th graders).

Generally we prep. beforehand by reading through the material and making sure there are no surprises. Well… Leslie preps first, and then manages to exercise supreme patience with me as I procrastinate reading through the material until the last minute.

This past week we were talking about the story of Naaman being cured of leprosy, and one of the activies included an activity sheet for the kids to fill out while I was reading the story. At different checkpoints, they’d have different activities to do—solve a puzzle, decipher a code, draw a picture, etc. The activity related to the segment of the story we’d just talked about.

One of the activies was to solve the equation I showed earlier:

9 * 7 = ____ + 7 = ____

with the solution being the amount (in kg) of gold that Naaman sent to the king of Israel to convince him to help (the amount of gold, of course, being critical for kids to know). I’d glanced at the equation during my hasty prep. and knew how I’d go about solving it. Since some of the other activities were a little too easy, I thought this would be a nice diversion into something a little more challenging. When we got to it the kids were confused, so I grabbed the whiteboard marker and wrote the equation on the board.

My first step, of course, was to solve what I could. This being a series of equations, I started off like this:

9 * 7 = ____ + 7 = _63_

I drew a helpful arrow over from the left equation to the right equation, to show that they must be equal. (At this point, Leslie started to give me funny looks, and the kids were looking a little confused but I soldiered on—math!)

The next step is of course to solve for the final unknown:

9 * 7 = _56_ + 7 = _63_

and