Answer:There are 13 more blocks he must walk before arriving at school.
Explanation:
Since we have given that
Number of blocks he has walk to the gallery = 4
Number of blocks he has walk to the museum = 10
Number of blocks he has walk to arrive at the school = 7
So, Total number of blocks becomes

Number of blocks he already walked = 8
so, remaining blocks would be

Hence, there are 13 more blocks he must walk before arriving at school.