diff --git a/exam/ex.tex b/exam/ex.tex
index c1c3dc4..0ac2c4d 100644
--- a/exam/ex.tex
+++ b/exam/ex.tex
@@ -282,7 +282,7 @@
       the challenge by $V$ is $ch^*$ (so $ch=ch^*$), $\mathcal{V}$ accepts,
       otherwise it rejects. Because $ch\in\{0,\dots,2^{130}-1\}$, the
       probability that $\mathcal{P}$ convinces $\mathcal{V}$ is
-      $\frac{1}{2^{130}}$ (soundness error).
+      $1/2^{130}$ (soundness error).
       
 
     \item \TODO