(-1) - (+1.2) - (+3.5) = -1 - 1.2 - 3.5 = -2.2 - 3.5 = -5.7
(+25.6) - (15.4) - (-10) - (-5.2) = 25.6 - 15.4 + 10 + 5.2 = 10.2 + 10 + 5.2 = 20.2 + 5.2 = 25.4
(-24.7) - (-14.7) - (-20) - (+11.26) = -24.7 + 14.7 + 20 - 11.26 = -10 + 20 - 11.26 = 10 - 11.26 = -1.26
$$\frac{|(-2) + (-8)|}{5} + \frac{3 - |-8|}{-5} = \frac{|-10|}{5} + \frac{3 - 8}{-5} = \frac{10}{5} + \frac{-5}{-5} = 2 + 1 = 3$$
(-18.2) + (-4.3) - (-25) + (+4.5) - (-3.7) - (+2.9) = -18.2 - 4.3 + 25 + 4.5 + 3.7 - 2.9 = -22.5 + 25 + 4.5 + 3.7 - 2.9 = 2.5 + 4.5 + 3.7 - 2.9 = 7 + 3.7 - 2.9 = 10.7 - 2.9 = 7.8