You need to find the value of a so solve the first equation in terms of y:

7a + y = -7
y = -7 - 7a

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

-8a - 1(-7 - 7a) = -7
-8a + (-1 x -7) + (-1 x -7a) = -7
-8a + 7 + 7a = -7
-8a + 7a = -7 - 7
-a = -14
a = \( \frac{-14}{-1} \)
a = 14

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

sa = 2πr² + 2πrh
sa = 2π(4²) + 2π(4 x 2)
sa = 2π(16) + 2π(8)
sa = (2 x 16)π + (2 x 8)π
sa = 32π + 16π
sa = 48π

The first step to solve a quadratic equation that's set to zero is to factor the quadratic equation:

z² - z - 42 = 0
(z + 6)(z - 7) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (z + 6) or (z - 7) must equal zero:

If (z + 6) = 0, z must equal -6
If (z - 7) = 0, z must equal 7

So the solution is that z = -6 or 7

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

a = l x w
a = a x b
a = 7 x 9
a = 63

Parallel lines are lines that share the same slope (steepness) and therefore never intersect. A transversal occurs when a set of parallel lines are crossed by another line. All of the angles formed by a transversal are called interior angles and angles in the same position on different parallel lines equal each other (a° = w°, b° = x°, c° = z°, d° = y°) and are called corresponding angles. Alternate interior angles are equal (a° = z°, b° = y°, c° = w°, d° = x°) and all acute angles (a° = c° = w° = z°) and all obtuse angles (b° = d° = x° = y°) equal each other. Same-side interior angles are supplementary and add up to 180° (e.g. a° + d° = 180°, d° + c° = 180°).