diff --git a/strings.Rmd b/strings.Rmd
index 80ee3daa..f6bd090a 100644
--- a/strings.Rmd
+++ b/strings.Rmd
@@ -405,7 +405,7 @@ Create a regular expression that will match telephone numbers as commonly writte
 
 <div class="answer">
 
-<div class="alert alert-primary hints-alert>
+<div class="alert alert-primary hints-alert">
 This answer can be improved and expanded.
 </div>
 
@@ -618,8 +618,8 @@ The answer to each part follows.
 Construct regular expressions to match words that:
 
 1.  Start and end with the same character.
-1.  Contain a repeated pair of letters (e.g. ``church'' contains ``ch'' repeated twice.)
-1.  Contain one letter repeated in at least three places (e.g. ``eleven'' contains three ``e''s.)
+1.  Contain a repeated pair of letters (e.g. ``church`` contains ''ch'' repeated twice.)
+1.  Contain one letter repeated in at least three places (e.g. ``eleven`` contains three ''e''s.)
 
 </div>
 
diff --git a/tidy.Rmd b/tidy.Rmd
index c125e573..9e4c606e 100644
--- a/tidy.Rmd
+++ b/tidy.Rmd
@@ -121,7 +121,7 @@ made it easy to divide cases by population.
 However, we had to repeat this calculation for each row.
 
 The ideal format of a data frame to answer this question is one with columns `country`, `year`, `cases`, and `population`.
-Then problem could be answered with a single `mutate()` call.
+Then, the problem could be answered with a single `mutate()` call.
 
 </div>