fix: printf exercises

* Improvements to exercise solutions
* Fix grammar in exercise

07-printf/exercises/01-print-your-age/main.go

@@ -13,7 +13,7 @@ package main
 //  Print your age using Prinft
 //
 // EXPECTED OUTPUT
-//  My age is 30 years old.
+//  I'm 30 years old.
 //
 // NOTE
 //  You should change 30 to your age, of course.

07-printf/exercises/01-print-your-age/solution/main.go

@@ -10,5 +10,5 @@ package main
 import "fmt"
 
 func main() {
-	fmt.Printf("My age is %d years old.\n", 30)
+	fmt.Printf("I'm %d years old.\n", 30)
 }

07-printf/exercises/06-print-the-type/solution/main.go

@@ -10,5 +10,5 @@ package main
 import "fmt"
 
 func main() {
-	fmt.Printf("Type of %d is %T\n", 3, 3)
+	fmt.Printf("Type of %d is %[1]T\n", 3)
 }

07-printf/exercises/07-print-the-type-2/solution/main.go

@@ -10,5 +10,5 @@ package main
 import "fmt"
 
 func main() {
-	fmt.Printf("Type of %f is %T\n", 3.14, 3.14)
+	fmt.Printf("Type of %.2f is %[1]T\n", 3.14)
 }

07-printf/exercises/08-print-the-type-3/solution/main.go

@@ -10,5 +10,5 @@ package main
 import "fmt"
 
 func main() {
-	fmt.Printf("Type of %s is %T\n", "hello", "hello")
+	fmt.Printf("Type of %s is %[1]T\n", "hello")
 }

07-printf/exercises/09-print-the-type-4/solution/main.go

@@ -10,5 +10,5 @@ package main
 import "fmt"
 
 func main() {
-	fmt.Printf("Type of %t is %T\n", true, true)
+	fmt.Printf("Type of %t is %[1]T\n", true)
 }