q)
1000 - [ 9 × 4 + 3 × 6 × 3 - ( a : 3 + 15 ) ] : 3 = 976
1000 - [ 36 + 18 × 3 - ( a : 3 + 15 ) ] : 3 = 976
1000 - [ 36 + 54 - ( a : 3 + 15 ) ] : 3 = 976
1000 - [ 90 - ( a : 3 + 15 ) ] : 3 = 976
[ 90 - ( a : 3 + 15 ) ] : 3 = 1000 - 976
[ 90 - ( a : 3 + 15 ) ] : 3 = 24
[ 90 - ( a : 3 + 15 ) ] = 24 × 3
[ 90 - ( a : 3 + 15 ) ] = 72
a : 3 + 15 = 90 - 72
a : 3 + 15 = 18
a : 3 = 18 - 15
a : 3 = 3
a = 3 × 3
a = 9