{ [ ( 6 - a ) × 2 - 7 ] × 9 - 5 } : 2 = 2
{ [ ( 6 - a ) × 2 - 7 ] × 9 - 5 } = 2 × 2
[ ( 6 - a ) × 2 - 7 ] × 9 - 5 = 4
[ ( 6 - a ) × 2 - 7 ] × 9 = 4 + 5
[ ( 6 - a ) × 2 - 7 ] × 9 = 9
( 6 - a ) × 2 - 7 = 9 : 9
( 6 - a ) × 2 - 7 = 1
( 6 - a ) × 2 = 1 + 7
( 6 - a ) × 2 = 8
6 - a = 8 : 2
6 - a = 4
a = 6 - 4
a = 2