𝑎⃗ = (−7,9)
𝑏⃗⃗ = (10,2)
𝑐⃗ = (1, −4)
(𝑎⃗ + 𝑏⃗⃗) + 𝑐⃗ = 𝑎⃗ + (𝑏⃗⃗ + 𝑐⃗)
[(-7,9)+(10,2)]+(1,-4)=(-7,9)+[(10,2)+(1,-4)]
(3,11)+(1,-4)=(-7,9)+(11,-2)
(4,7)=(4,7)