Question

[676:13:(31·20-31-a)]·45- 23·91=247

Answer 1

[676:13:(31×20-31-a)]×45-23×91=247
[52:(31×19-a)]×45-2093=247
[52:(589-a)]×45=247+2093
[52:(589-a)]×45=2340
52:(589-a)=52
589-a=1
a=589 -1
a=588

Answer 2

[676:13:(31×20-31-a)]×45-23×91=247
[52:(610-31-a)]×45-2093=247
[52:(579-a)]×45=2093+247
[52:(579-a)]×45=2340
52:(579-a)=2340:45
52:(579-a)=52
579-a=x
52:x=52
x=52:52
x=1
597-a=1
a=597-1
a=596