Question

28-[19-{11-(7-6+?)}]

Answer 1

let ? be x
28-[19-{11-(7-6+x)}]=9
28 = 9+[19-{11-(7-6+x)}]
28-9 = 19-{11-(7-6+x)}
19 = 19-{11-(7-6+x)}
19+{11-(7-6+x)}=19
11-(7-6+x)=19-19
11-(7-6+x) =0
11=7-6+x
11=1+x
x=10

Answer 2

28 - [ 19 - { 11 - ( 7 - 6 + ? )}]

by trial method

let' ?' be "x "

substituting "x "in ?

28 - [ 19 - { 11 - ( 7 - 6 + x )}] = 0

28 - [ 19 - { 11 - (1 + x )}] = 0

28 - [ 19 - { - 11 - 11 x }] = 0

28 - [ 19 + 11 + 11 x ] = 0

28 - 30 + 11 x = 0

- 2 + 11 x = 0

11 x = 2

× = 2/11