Question

|5y+10|=55

Answer 1

5y=45 -5y=65
y=9 y=-65/5

Answer 2

I think it makes more sense to set it up as
5y+10 = 55 5y+10=-55
5y=45 5y=-65
y=9 y=-13

That way you stick with the idea that an absolute value is the positive and negative value.

Answer 3

9,-13