CHALLENGE 1: Type the Parameters
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SOLUTION:

function add(a: number, b: number): number {
  return a + b;
}

EXPLANATION:
- "a: number" means parameter 'a' must be a number
- "b: number" means parameter 'b' must be a number
- ": number" after the closing parenthesis means the function returns a number
- Now add("5", 3) will produce a TypeScript error:
  Error: Argument of type 'string' is not assignable to parameter of type 'number'

ADDITIONAL NOTES:
- You could also write it inline: function add(a: number, b: number) { ... }
- TypeScript will infer the return type is 'number' if you omit ": number"
- But explicitly typing the return value is good practice — it documents intent

TESTING:
add(5, 3)           // ✅ Works: returns 8
add("5", 3)         // ❌ TypeScript error immediately
add(5, 3, 2)        // ❌ Too many arguments