Challenge 1: Func<int,int,int> and Action<string> — Possible Solution
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Program.cs:

Func<int, int, int> multiply = (a, b) => a * b;
Action<string> announce = msg => Console.WriteLine(msg);

int result = multiply(6, 7);
announce($"6 * 7 = {result}");

Output:

    6 * 7 = 42

Explanation:
multiply is a Func<int, int, int> -- the LAST type parameter (int) is
the return type, and the first two (int, int) are the parameter
types, exactly matching the chapter's own Func<int, int, int>
pattern. announce is an Action<string> -- it takes a string and
returns nothing, so no return-type parameter is needed at all.
Calling multiply(6, 7) invokes the lambda directly through the
delegate, producing 42, which announce then prints.

WHY THIS WORKS AS AN ANSWER
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This uses both built-in delegate types exactly as the chapter
introduces them, correctly placing the return type last in Func's
type parameter list and confirming Action's void-returning shape.