Counting in groups of 7's, 14's, 30s for everyday use. Study the examples below carefully, and answer the questions below by finding the missing numbers in the diagram.

In the given examples, the sum of the two numbers in the top row is equal to the sum of the two numbers in the bottom row.
For example 1: $6 + 24 = 30$ and $12 + 18 = 30$.
For example 2: $12 + 30 = 42$ and $18 + 24 = 42$.
This pattern will be used to find the missing numbers.

Given: Top numbers are 12 and 21. Bottom numbers are 15 and a missing number.
Sum of top numbers: $12 + 21 = 33$.
Let the missing number be $x$.
Sum of bottom numbers: $15 + x$.
According to the pattern: $15 + x = 33$.
$x = 33 - 15 = 18$.
The student's answer is correct.

Given: Top numbers are 14 and a missing number. Bottom numbers are 21 and 28.
Sum of bottom numbers: $21 + 28 = 49$.
Let the missing number be $x$.
Sum of top numbers: $14 + x$.
According to the pattern: $14 + x = 49$.
$x = 49 - 14 = 35$.
The student's answer is correct.

Given: Top numbers are 60 and 240. Bottom numbers are 120 and a missing number.
Sum of top numbers: $60 + 240 = 300$.
Let the missing number be $x$.
Sum of bottom numbers: $120 + x$.
According to the pattern: $120 + x = 300$.
$x = 300 - 120 = 180$.
The student's answer is correct.

Given: Top numbers are 60 and 90. Bottom numbers are a missing number and 80.
Sum of top numbers: $60 + 90 = 150$.
Let the missing number be $x$.
Sum of bottom numbers: $x + 80$.
According to the pattern: $x + 80 = 150$.
$x = 150 - 80 = 70$.
The student's answer is correct.

Given: Top numbers are 10 and 25. Bottom numbers are a missing number and 20.
Sum of top numbers: $10 + 25 = 35$.
Let the missing number be $x$.
Sum of bottom numbers: $x + 20$.
According to the pattern: $x + 20 = 35$.
$x = 35 - 20 = 15$.
The student's answer is correct.

Given: Top numbers are 100 and a missing number. Bottom numbers are 150 and 200.
Sum of bottom numbers: $150 + 200 = 350$.
Let the missing number be $x$.
Sum of top numbers: $100 + x$.
According to the pattern: $100 + x = 350$.
$x = 350 - 100 = 250$.
The student's answer is correct.