Duru and her friend Efe were two brave kids who always liked to embark on new adventures. One day, while they were walking on the beach, they found a shining bottle on the seashore. Inside the bottle was an old paper. Both of them excitedly opened the bottle and examined the paper carefully. It looked like a treasure map.

It said: “Welcome to Math Island. Find the missing numbers and restore the island to its former state. If you succeed, a great reward awaits you!”  Duru and Efe looked at each other. Both were determined to embark on this adventure. They set off in a small boat towards the place the map indicated. In the distance, an island was visible hidden among the clouds. Here was the Mathematics Island! 

When they arrived at the shore of the island, an old turtle welcomed them. The turtle could talk! “Welcome, brave travelers,” said the turtle. “The island’s numbers were stolen by an evil wizard named Karabas. Without the numbers, life here has come to a standstill. Our mission is to solve the addition operations set to bring the numbers back. If you succeed, you can reach the treasure.” Duru and Efe nodded resolutely. The turtle gave them a map of the island and directed them to their first mission.

They arrived at a beach covered with golden sand. In front of them stood a large stone door with the following inscription: “To open this door, solve this operation: 1567 + 2438 = ?” 

Efe immediately started doing the calculation: Ones place: 7 + 8 = 15, carry 1. Tens place: 6 + 3 = 9, also carry 1, and obtain 10. Carry 1. Hundreds place: 5 + 4 = 9, also carry, 10. Carry 1. Thousands place: 1 + 2 = 3, also carry, 4. "The result is 4005!" said Efe. The door opened with a loud noise and a bright light spilled in. Inside was a chest, and inside the chest were the first missing numbers.

According to the map, the next stop was the Shadow Forest. Deep in the forest, it was said that a mysterious tree with numbers waited. Among the twisted branches, they found a sign that read: “To revive the tree, solve the following equation: 2765+349=?”

Duru and Efe started to solve it together:  Ones place: 5 + 9 = 14, carry 1. Tens place: 6 + 4 = 10, also carry, 11. Carry 1. Hundreds place: 7 + 3 = 10, also carry, 11. Carry 1. Thousands place: 2 + 0 = 2, also carry, 3. “The result is 3114!” they said. Suddenly the tree came to life, its leaves began to shine, and a golden cube fell from its trunk. Inside the cube were the second missing numbers.

The third stop on the map was marked as Crystal Lake, located in the center of the island. They reached a floating platform in the middle of the lake. On the platform was a large crystal that illuminated the lake. However, there was a riddle on the crystal: “To activate the crystal, solve the following: 3789 + 5423 = ?”