01-intro.md: rephrase the "Check Your Understanding" question (#861)

Author: n-frazee

_episodes/01-intro.md

@@ -181,21 +181,23 @@ weight in kilograms is now: 65.0
 
 > ## Check Your Understanding
 >
-> What values do the variables `mass` and `age` have after each statement in the following program?
-> Test your answers by executing the commands.
+> What values do the variables `mass` and `age` have after each of the following statements? 
+> Test your answer by executing the lines.
 >
 > ~~~
 > mass = 47.5
 > age = 122
 > mass = mass * 2.0
 > age = age - 20
-> print(mass, age)
 > ~~~
 > {: .language-python}
 >
 > > ## Solution
 > > ~~~
-> > 95.0 102
+> > `mass` holds a value of 47.5, `age` does not exist
+> > `mass` still holds a value of 47.5, `age` holds a value of 122
+> > `mass` now has a value of 95.0, `age`'s value is still 122
+> > `mass` still has a value of 95.0, `age` now holds 102
 > > ~~~
 > > {: .output}
 > {: .solution}