The pattern in this puzzle takes the first number and multiplies it by the sum of the two numbers. You can think of the rule as A × (A + B).
Let’s test this rule on the given equations:
1 + 2 = 3: 1 × (1 + 2) = 1 × 3 = 3
3 + 4 = 21: 3 × (3 + 4) = 3 × 7 = 21
5 + 6 = 55: 5 × (5 + 6) = 5 × 11 = 55
Applying this exact pattern to the final equation: