The line segment is reflected about the y-axis to form a'b'. which statement describes a'b'?

(Please correct me if I'm reading one of the numbers wrong.)

-5.8 + 2.6

We can rewrite this equation so it's easier to read like this:

2.6 - 5.8 (the answer will still be the same)

In the original equation, you're simply adding 2.6 to -5.8.

In the new equation, you're taking 5.8 away from 2.6.

An easy way to solve this is to ask "what's the difference between 5.8 and 2.6?", which is 3.2.

The answer to this problem is -3.2, because we're taking a larger number away from a smaller number.