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:

(y + 7)(y - 3)
(y x y) + (y x -3) + (7 x y) + (7 x -3)
y² - 3y + 7y - 21
y² + 4y - 21

The area of a trapezoid is one-half the sum of the lengths of the parallel sides multiplied by the height:

a = ½(b + d)(h)
a = ½(9 + 8)(4)
a = ½(17)(4)
a = ½(68) = \( \frac{68}{2} \)
a = 34

The area of a rectangle is equal to its length x width:

a = l x w
a = a x b
a = 5 x 3
a = 15

The surface area of a cylinder is 2πr² + 2πrh:

sa = 2πr² + 2πrh
sa = 2π(9²) + 2π(9 x 7)
sa = 2π(81) + 2π(63)
sa = (2 x 81)π + (2 x 63)π
sa = 162π + 126π
sa = 288π

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

7b + z = -5
z = -5 - 7b

then substitute the result (-5 - 7b) into the second equation:

7b - 2(-5 - 7b) = -4
7b + (-2 x -5) + (-2 x -7b) = -4
7b + 10 + 14b = -4
7b + 14b = -4 - 10
21b = -14
b = \( \frac{-14}{21} \)
b = -\(\frac{2}{3}\)