2 целых 7/15 = 2 + 7/15 = 2 + 0.4666... = 2.4666...1 целая 1/12 = 1 + 1/12 = 1 + 0.0833... = 1.0833...2 целых 7/90 = 2 + 7/90 = 2 + 0.0777... = 2.0777...1 целая 1/2 = 1 + 1/2 = 1 + 0.5 = 1.58 целых 8/45 = 8 + 8/45 = 8 + 0.1777... = 8.1777...

Итак, подставляя значения:
2.4666... - 1.0833... + (2.0777... - (1.5 - 8.1777...)) =
= 2.4666 - 1.0833 + (2.0777 - (1.5 - 8.1777)) =
= 1.3833 + (2.0777 - (-6.6777)) =
= 1.3833 + (2.0777 + 6.6777) =
= 1.3833 + 8.7554 =
= 10.1387

Итак, значение выражения равно 10.1387.