1 + 9 + 2 + 8 = ( 1 + 9 ) + ( 2 + 8 )
= 10 + 10
= 20
1 + 9 + 2 + 8
= 10 + 2 + 8
= 12 + 8
= 20
1 + 9 + 2 + 8
= (1 + 9) + (2 + 8)
= 10 + 10
= 10 x 2
= 20
1 + 9 + 2 + 8
= 10 + 2 + 8
= 12 + 8
= 20
1 + 9 + 2 + 8
= (1 + 9) + (2 + 8)
= 10 + 10
= 10 x 2
= 20
1 + 9 + 2 + 8
= ( 1 + 9 ) + ( 2 + 8 )
= 10 + 10
= 20