[ 936 - ( 8 × 100 + a ) ] : [ 10 + ( 35 : 5 + 8 ) ] = 4
[ 936 - ( 800 + a ) ] : [ 10 + ( 7 + 8 ) ] = 4
[ 936 - ( 800 + a ) ] : ( 10 + 15 ) = 4
[ 936 - ( 800 + a ) ] : 25 = 4
936 - ( 800 + a ) = 4 × 25
936 - ( 800 + a ) = 100
800 + a = 936 - 100
800 + a = 836
a = 836 - 800
a = 36
