A circle is a figure in which each point around its perimeter is an equal distance from the center. The radius of a circle is the distance between the center and any point along its perimeter. A chord is a line segment that connects any two points along its perimeter. The diameter of a circle is the length of a chord that passes through the center of the circle and equals twice the circle's radius (2r).

The circumference of a circle is the distance around its perimeter and equals π (approx. 3.14159) x diameter: c = π d. The area of a circle is π x (radius)² : a = π r².

Angles around a line add up to 180°. Angles around a point add up to 360°. When two lines intersect, adjacent angles are supplementary (they add up to 180°) and angles across from either other are vertical (they're equal).

You need to find the value of b so solve the first equation in terms of z:

5b + z = -6
z = -6 - 5b

then substitute the result (-6 - 5b) into the second equation:

4b + 3(-6 - 5b) = -5
4b + (3 x -6) + (3 x -5b) = -5
4b - 18 - 15b = -5
4b - 15b = -5 + 18
-11b = 13
b = \( \frac{13}{-11} \)
b = -1\(\frac{2}{11}\)

To multiply binomials, use the FOIL method. FOIL stands for First, Outside, Inside, Last and refers to the position of each term in the parentheses.