When heads is greater than tails = (No. of head = 7) + (No. of head = 6) + (No. of head = 5) + (No. of head = 4)

No. of head is 7 $={}^7C_7=1$

No. of heads is 6 $={}^7C_6=7$

No. of heads is 5 $={}^7C_5=21$

No. of heads is 4 $={}^7C_4=35$

Required Probability = $\frac{favourable}{total\,possible}=\frac{1+7+21+35}{2^7}=\frac{64}{128}=\frac{1}{2}$

Correct me if I'm wrong