Explanation:
let's simplify first :
-1.3 + (-4.9) + (-2.6) = -1.3 - 4.9 - 2.6
let's look at the simplifications of the answer options and compare :
-1.3 - (4.9 + 2.6) = -1.3 - 4.9 - 2.6 correct !
-1.3 + (4.9 + 2.6) = -1.3 + 4.9 + 2.6 wrong !
-(1.3 - 4.9) + (-2.6) = -1.3 + 4.9 - 2.6 wrong !
(1.3 + 4.9 + 2.6) = 1.3 + 4.9 + 2.6 wrong !