This is an Inclusion-Exclusion (Overlapping Sets) problem, and the key is setting up one variable smartly using the ratio relationship given in the problem. The trap most students fall into is trying to use the full Venn diagram formula (L + C + P - both pairs + all three + none = total) without first noticing that the problem gives you a clean ratio between "at least two" and "none."
Key concept: Inclusion-Exclusion with a bridging ratio.
Let x = number of people who bought at least two legumes.
Then: people who bought all three = x/3 (one-third of "at least two")
And: people who bought none = 2x (two people bought none for every one who bought at least 2)
Step 1: Use the identity for the sum of individual group counts.
L + C + P = (exactly 1) + 2(exactly 2) + 3(all three)
36 + 37 + 35 = 108
Step 2: Express the sub-groups in terms of x.
Exactly 2 = x - x/3 = 2x/3
All three = x/3
So: 108 = (exactly 1) + 2(2x/3) + 3(x/3) = (exactly 1) + 4x/3 + x = (exactly 1) + 7x/3
Step 3: Use the total to express "exactly 1" in terms of x.
Total = (exactly 1) + (at least 2) + none
120 = (exactly 1) + x + 2x
→ exactly 1 = 120 - 3x
Step 4: Substitute into the equation from Step 2.
108 = (120 - 3x) + 7x/3
108 - 120 = -3x + 7x/3 = x(-9/3 + 7/3) = -2x/3
-12 = -2x/3
x = 18
Step 5: Calculate "none."
None = 2x = 2(18) = 36
Quick check: exactly 1 = 120 - 3(18) = 66; exactly 2 = 12; all three = 6
Total = 66 + 12 + 6 + 36 = 120 ✓
L + C + P = 66 + 2(12) + 3(6) = 66 + 24 + 18 = 108 ✓
Answer: C (36)
Takeaway: In three-set Overlapping Sets problems, always look for a ratio relationship connecting your unknowns — it lets you work with one variable instead of three, and the problem unravels very quickly.