one day, the northwest woodworks studio produced six times as many bookshelves as the southeast woodworking guild. If the difference in their production is 15, how many bookshelves did the southeast woodworking guild produce that day?

Answer 1

If the south guild produced x, then the north guild produced 6x. Now, what else do we know?
6x - x = 15
now just crank it out

Answer 2

Southeast = X bookshelves.
Northwest = 6x bookshelves.

6x - x = 15.
X = ?