First digit can be chosen in $8$ ways from $1−9$ excluding $7$
Second digit can be chosen in $9$ ways from $0−9$ excluding $7$ and similarly the third digit in $9$ ways.
So, total no. of ways excluding $7 = 8\times 9\times 9$
Total no. of ways including $7 = 9\times 10\times 10$
So, answer $= \dfrac{(8\times 9\times 9)}{(9\times 10\times10)}=\dfrac{18}{25}$