<h2>
Answer:</h2>
1. D
2. B
3. E
4. C
5. B
<h2>Concept:</h2>
From the three examples at the top of the page, the sum of the bottom two parts of the triangle equals to six times the value of the part at the top.
For example, the first one: 20, 10, 5 (Tip)
For example, the second one: 4, 14, 3 (Tip)
<h2>Solve:</h2>
Question 1
<u>Given information</u>
Tip = 15
Bottom = ?, 51
<u>Determine the sum</u>
15 × 6 = 90
<u>Find the other bottom part</u>
90 - 51 = 39

Question 2
<u>Given information</u>
Tip = 9
Bottom = 21, ?
<u>Determine the sum</u>
9 × 6 = 54
<u>Find the other bottom part</u>
54 - 21 = 33

Question 3
<u>Given information</u>
Tip = ?
Bottom = 60, 60
<u>Determine the sum</u>
60 + 60 = 120
<u>Find the tip</u>
120 ÷ 6 = 20

Question 4
<u>Given information</u>
Tip = ?
Bottom = 18, 30
<u>Determine the sum</u>
18 + 30 = 48
<u>Find the tip</u>
48 ÷ 6 = 8

Question 5
<u>Given information</u>
Tip = 12
Bottom = ?, 38
<u>Determine the sum</u>
12 × 6 = 72
<u>Find the other bottom part</u>
72 - 38 = 34

Hope this helps!! :)
Please let me know if you have any questions