# Bug / Math Contradictions ("Error / x")

Some users find out that it is possible to reach a contradiction in some levels. In particular in DragonBox Algebra 12+, one can end up with 4 = 5 in Chapter 10 Level 7.

Here's the explanation given by Jean, creator of DragonBox, and math teacher too : )

*"On purpose we have designed levels where you happen to come to a
contradiction if you perform an operation that is actually illegal
when solving equations.
*

*
Our purpose with the game is to: *

*teach algebraic rules and manipulation**make players to actively think of strategies as how to solve the different puzzles**discover properties of equations*

*4=5 is I guess achievable because you [...] you divided by "0".
this can not be done for obvious reasons... We want the player to
discover it and ask questions instead of being told not to do it."*