crutches + coffee = disaster.
It was further argued (by another friend) that
coffee + disaster = crutches
This is very nice, but it seems to me,
disaster = crutches
just as well as
coffee + disaster = crutches.
The crutches are because of the disaster, not the coffee.
I think coffee + disaster = laundry
Now if we add crutches to each side,
coffee + crutches + disaster = crutches + laundry
This is believable. Now, if we substitute using the original expression, we obtain
2 disasters = crutches + laundry
This make sense. Crutches from, say, a car wreck, and laundry from spilling your coffee. Two separate disasters.
Someone also pointed out that
disaster + crutches does not necessarily equal coffee.
Well, that's because,
disaster - crutches = coffee.
Think about it. If you had a disaster and you didn't have any crutches, you'd be stuck in a chair all day. If that happened to me, I would definitely drink a lot of coffee. Also, if we add crutches to both sides, we get,
disaster = crutches + coffee, which is just a rearrangement of where we started.