typo fix 1.3 and centering 3.3

src/chap_one_percents.ptx

@@ -941,7 +941,7 @@
 <exercise><!--  #9 -->
 	<statement>
 	<p>
-		To help aleviate homelessness, voters in the Portland Metro area approved a personal income tax for individuals who make over $125,000 in taxable income. Miguel has a taxable income of $180,000 and the rate for that level of income is 1.5%. How much will Miguel owe for this tax?
+		To help alleviate homelessness, voters in the Portland Metro area approved a personal income tax for individuals who make over $125,000 in taxable income. Miguel has a taxable income of $180,000 and the rate for that level of income is 1.5%. How much will Miguel owe for this tax?
 	</p>
 	</statement>
 	<solution>

src/chap_three_measure_of_center.ptx

@@ -77,7 +77,7 @@
 			To find the mean test score we need to find the sum of her test scores, then divide the sum by the number of test scores (<m>n=4</m>). The mean is:
 		</p>
 		<p>
-			<m>\bar{x}=\frac{79+86+82+94}{4}=85.25</m> points
+			<me>\bar{x}=\frac{79+86+82+94}{4}=85.25\text{ points}</me>
 		</p>
 		<p>
 			We will round the sample mean to one more decimal place than the original data. In this case, we would round 85.25 to 85.3 points. Also notice that the mean has the same units as the data and it is important to label it.

src/index.ptx

@@ -39,11 +39,13 @@
 		 should ulimately be explicit support for an image like this on the landing page. -->
 		<introduction>
 			<!-- Todo: Edition change -->
+			<!-- Edition 1 cover image -->
 			<!-- <p>
 				<image source="images/Portland_Oregon_Skyline.jpg">
 				<shortdescription>A picture of the Portland, Oregon skyline taken from the Ross Island Bridge</shortdescription>
 			</image> -->
 			<!-- </p> -->
+			<!-- Edition 2 cover image -->
 			<p>
 				<image source="images/Good_Morning_Portland.jpg">
 				<shortdescription>A picture of the Hawthorne Bridge toward downtown Portland, Oregon</shortdescription>
@@ -55,7 +57,6 @@
 <!-- Select correct Chapter 1 sections in this file according to edition -->
 		<xi:include href="./logic_problem_solving.ptx" />
 <!-- Chapters 2-5 same in both editions -->
-
 		<xi:include href="./financial_math.ptx" />
 		<xi:include href="./statistics.ptx" />
 		<xi:include href="./probability.ptx" />