Numbers are given, which you must put in the square. The main condition is to use 3 different numbers from the given four.

Summary:

Equations:

• Equation 1: + + = 15
• Equation 2: + + = 18

Solution:

• For Equation 1 (sum = 15): We need to choose three different numbers from {4, 5, 6, 7} that add up to 15. The combination 4 + 5 + 6 = 15 satisfies this condition.
• For Equation 2 (sum = 18): We need to choose three different numbers from the *remaining* set, or a different combination if we are allowed to reuse numbers from the original set. Given the numbers in the image, it seems we need to fill the blanks using the provided numbers. Let's assume the numbers are 4, 5, 6, 7.
• If we use 4, 5, 6 for the first equation (4+5+6=15), then for the second equation, we can use 5, 6, 7 (5+6+7=18). Both equations use 3 different numbers from the given set, and the numbers used in each equation are distinct from each other within that equation.

Answer: For the first equation, the numbers are 4, 5, 6. For the second equation, the numbers are 5, 6, 7.