TL ;
12:{400:[500-(125+25.7)]}
= 12 : { 400 : [ 500 - ( 125 + 175 )]}
= 12 : { 400 : 200 }
= 12 : 2
= 6
\(12\div\left\{400\div\left[500-\left(125+25.7\right)\right]\right\}\)
\(=\)\(12\div\left\{400\div\left[500-\left(125+175\right)\right]\right\}\)
\(=\)\(12\div\left\{400\div\left[500-300\right]\right\}\)
\(=\)\(12\div\left\{400\div200\right\}\)
\(=\)\(12\div2\)
\(=\)\(6\)