54 - 4 × 3 : [ 2 × 11 - 5 - ( 5 × 4 - a ) ] + 14 × 2 = 76
54 - 12 : [ 22 - 5 - ( 20 - a ) ] + 28 = 76
54 - 12 : [ 17 - ( 20 - a ) ] = 76 - 28
54 - 12 : [ 17 - ( 20 - a ) ] = 48
12 : [ 17 - ( 20 - a ) ] = 54 - 48
12 : [ 17 - ( 20 - a ) ] = 6
17 - ( 20 - a ) = 12 : 6
17 - ( 20 - a ) = 2
20 - a = 17 - 2
20 - a = 15
a = 20 - 15
a = 5
