Add clarification for the exercises delete_prefix and lalgebra_vector

subjects/delete_prefix/README.md

@@ -2,7 +2,7 @@
 
 ### Instructions
 
-Define the function `delete_prefix(prefix, s)` which returns the string slice `s` with the `prefix` removed wrapped in `Some`. If `prefix ` is not contained in `s` it returns `None`.
+Define the function `delete_prefix(prefix, s)` which returns the string slice `s` with the `prefix` removed wrapped in `Some`. If `prefix ` is not a prefix of `s` it returns `None`.
 
 ### Expected Function
 

subjects/lalgebra_vector/README.md

@@ -4,7 +4,7 @@
 
 A vector in linear algebra is defined as "anything that can be added and that can be multiplied by a scalar"
 
-And the associated function dot that calculates the dot product between two vectors
+Define the associated function `dot` that calculates the dot product between two vectors
 
 The dot product between two vectors of different length it's not defined