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

-6b + z = 4
z = 4 + 6b

then substitute the result (4 - -6b) into the second equation:

-6b + 5(4 + 6b) = 8
-6b + (5 x 4) + (5 x 6b) = 8
-6b + 20 + 30b = 8
-6b + 30b = 8 - 20
24b = -12
b = \( \frac{-12}{24} \)
b = -\(\frac{1}{2}\)

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.

To solve this equation, repeatedly do the same thing to both sides of the equation until the variable is isolated on one side of the < sign and the answer on the other.

-4a + 2 < \( \frac{a}{-6} \)
-6 x (-4a + 2) < a
(-6 x -4a) + (-6 x 2) < a
24a - 12 < a
24a - 12 - a < 0
24a - a < 12
23a < 12
a < \( \frac{12}{23} \)
a < \(\frac{12}{23}\)

An exterior angle of a triangle is equal to the sum of the two interior angles that are opposite:

d° = b° + c°

To find angle c, remember that the sum of the interior angles of a triangle is 180°:

180° = a° + b° + c°
c° = 180° - a° - b°
c° = 180° - 33° - 69° = 78°

So, d° = 69° + 78° = 147°

A shortcut to get this answer is to remember that angles around a line add up to 180°:

a° + d° = 180°
d° = 180° - a°
d° = 180° - 33° = 147°

To multiply monomials, multiply the coefficients (the numbers that come before the variables) of each term, add the exponents of like variables, and multiply the different variables together.

(6a)(5ab) - (4a²)(8b)
(6 x 5)(a x a x b) - (4 x 8)(a² x b)
(30)(a¹⁺¹ x b) - (32)(a²b)
30a²b - 32a²b
-2a²b