make learning goals more specific

src/index.md

@@ -5,8 +5,8 @@
     After following this course you will be able to:
 
     - Formulate the main models of solid state physics
-    - Given a problem description, write down the corresponding equations
-    - Identify the relevant approximations and solve these problems
+    - Given a description of a solid state physics problem, write down the corresponding equations
+    - Identify the relevant approximations and apply them to solve this problem
 
 In these notes our aim is to provide learning materials which are: