Answer:
Step-by-step explanation:
1. ⁷C₅ = ⁷C₂ = 7 x 6 / 2 = 21
2. ⁹C₈ = ⁹C₁ = 9
3. ¹²C₅ = 12 x 11 x 10 x 9 x 8 / 2 x 3 x 4 x 5
= 11 x 9 x 8 = 11 x 72 = 792
4. ²⁰C₁₇ = ²⁰C₃ = 20 x 19 x 18 / 2 x 3
= 19 x 3 = 57
5. ¹⁶C₁₃ = ¹⁶C₃ = 16 x 15 x 14 / 2 x 3
= 8 x 5 x 14 = 40 x 14 = 560
6. ⁷C₄ + ¹¹C₉ = ⁷C₃ + ¹¹C₂ = (7 x 6 x 5 / 2 x 3) + (11 x 10 / 2)
= 35 + 55 = 90
7. ⁷C₃ + ⁷C₄ + ⁷C₅ = 2(⁷C₃) + ⁷C₂ = (2 x 7 x 6 x 5 / 2 x 3) + (7 x 6 / 2)
= 70 + 21 = 91
Legit only this much I can do now.
Hope it is enough.
