\(12:\left\{390:\left[500-\left(5^3+7^2.5\right)\right]\right\}\)
\(=12:\left\{390:\left[500-\left(125+49.5\right)\right]\right\}\)
\(=12:\left\{390:\left[500-\left(125+245\right)\right]\right\}\)
\(=12:\left[390:\left(500-370\right)\right]\)
\(=12:\left(390:130\right)\)
\(=12:3\)
\(=4\)
12 : { 390 : [ 500 - ( 53 + 72 . 5 ) ] }
= 12 : { 390 : [ 500 - (125 + 49 . 5 ) ] }
= 12 : { 390 : [ 500 - (125 + 245 ) ] }
= 12 : { 390 : [ 500 - 370] }
= 12 : { 390 : 130}
= 12 : 3
= 4
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