-- Draw a line from the center of the circle to the left end of the horizontal chord. (That point doesn't have an identification letter, but it's the other end of the '10' from point 'A'.)
-- Since that line is also a radius of the circle, its length is 14.5 .
-- When you drew the line, you made a right triangle inside the circle. The line you drew is the hypotenuse of the right triangle.
-- You know the length of the hypotenuse (14.5), and you know the length of one leg (10). So you can calculate the length of the other leg ... from the center to point 'A'. That leg is √(14.5² - 10²)
-- Now you know the distance from the center of the circle to point 'A'. The length of AB is (the radius) minus (the leg that you just found).
Seem reasonable ?
I got 4 for AB. But I was working fast and sloppy. You need to check it.
The expression –3 + 2x is equivalent to 2x – 3. I know it is equivalent because for every value of x that is substituted in, the two expressions simplify to the same value. I took the expression and used the commutative property to not change the value.