What value of x makes 2x-1=-7 true?

In the diagram of circle o, what is the measure of zabc?

Select all of the following expressions that are equal to 2.5.

A6 ounce bottle of dressing costs $1.56 a 14 ounce bottle costs $3.36 a 20 ounce bottle costs $5.60 which has the lowest cost per ounce