Update HOME_EXAM.md

HOME_EXAM.md

@@ -237,7 +237,9 @@ Not sure how to do this for elseif
 **while** statement:
 ```math
 \frac{\lang b, \sigma \rang \ \Downarrow \ \text{false} \quad \lang c, \sigma \rang \Downarrow \sigma' }{\text{while } b \text{ do } c, \sigma \rang \ \Downarrow \ \sigma}
+```
 
+```math
 \frac{\lang b, \sigma \rang \ \Downarrow \ \text{true} \quad \lang c, \sigma \rang \ \Downarrow \ \sigma' \quad \lang \text{while } b \text{ do } c,\sigma' \rang \ \Downarrow \ \sigma''}{\lang \text{while } b \text{ do } c, \sigma \rang \ \Downarrow \ \sigma''}
 ```