Concept exercise review: lasagna (JuliaLang#433)

* Make lasagna hint appear

* Fix accidental double word

* Add some more hints

* Apply suggestions from code review

Co-authored-by: Sascha Mann <git@mail.saschamann.eu>

exercises/concept/lasagna/.docs/hints.md

@@ -1,6 +1,21 @@
-# General
+# Hints 
 
-You will need to define [functions][functions] and use [arithmetic operators][arithmetics].
+## General
+
+- You will need to define [functions][functions] and use [arithmetic operators][arithmetics].
+
+## 1. Calculate the preparation time in minutes
+
+- Use the [`times` arithmetic operator][arithmetics] to multiply the argument by `2`.
+
+## 2. Calculate the remaining oven time in minutes
+
+- Use the [`minus` arithmetic operator][arithmetics] to subtract the argument from `60`.
+
+## 3. Calculate the total working time in minutes
+
+- Reuse the `preptime` function defined in the first step.
+- Use the [`plus` arithmetic operator][arithmetics] to add the return value of `preptime` to the argument.
 
 [functions]: https://docs.julialang.org/en/v1/manual/functions/
 [arithmetics]: https://docs.julialang.org/en/v1/manual/mathematical-operations/#Arithmetic-Operators-1

exercises/concept/lasagna/.docs/introduction.md

@@ -40,7 +40,7 @@ square_plus_one(x) = muladd(x, x, 1)
 ### Types
 
 Depending on which other programming languages you know, you may expect parameters, variables or return values to have explicit type annotations.
-For now, assume that that Julia will infer the types automagically and don't worry about them, we will get to the specifics of the type system in later exercises.
+For now, assume that Julia will infer the types automagically and don't worry about them, we will get to the specifics of the type system in later exercises.
 
 ### Comments