We know, area under the velocity-time graph represents displacement of particle.
D𝑖𝑠𝑝𝑙𝑎𝑐𝑒𝑚𝑒𝑛𝑡 𝑜𝑓 𝑡ℎ𝑒 𝑝𝑎𝑟𝑡𝑖𝑐𝑙𝑒 𝑖𝑛 6 𝑠𝑒𝑐𝑜𝑛𝑑𝑠 = 𝐴𝑟𝑒𝑎 𝑜𝑓 𝑡ℎ𝑒 𝑡𝑟𝑖𝑎𝑛𝑔𝑙𝑒 𝑓𝑜𝑟𝑚𝑒𝑑 𝑏𝑦 𝑣𝑒𝑙𝑜𝑐𝑖𝑡𝑦 𝑡𝑖𝑚𝑒 𝑔𝑟𝑎𝑝ℎ 𝑎𝑛𝑑 𝑡𝑖𝑚𝑒 𝑎𝑥𝑖𝑠
=12×6s×2ms−1
=6 𝑚
Hence, the displacement of a particle at t =6 s is 6 m.