18 . [(8x + 10 ) : 5] + 12 = 490
18 . [(8x + 10 ) : 5] = 490 - 12
18 . [(8x + 10 ) : 5] = 478
[(8x + 10 ) : 5] = 478 : 18
( 8x + 10 ) : 5 = \(\frac{239}{9}\)
8x + 10 = \(\frac{239}{9}\) .5
8x + 10 = \(\frac{1195}{9}\)
8x = \(\frac{1195}{9}\) - 10
8x = \(\frac{1195}{9}-\frac{90}{9}\)
8x = \(\frac{1105}{9}\)
x = \(\frac{1105}{9}\)\(\div\)8
x = \(\frac{1105}{9}\) . \(\frac{1}{8}\)
x = \(\frac{1105}{72}\)