5+[200-184+(a:9x8+28:4)]x6=287
[200-184+(a:9x8+28:4)]x6=287-5
[ 16 +( a : 9 x 8 + 7) ]x6 = 282
16 + ( a : 9 x8 +7) = 282 : 6
16 + ( a : 9 x 8 +7) = 47
a : 9 x 8 + 7 = 47 - 16
a : 9 x 8 +7 = 31
a : 9 x 8 = 31 - 7
a : 9 x 8 = 24
a : 9 = 24 : 8
a : 9 = 3
a = 9 x 3
a = 27