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

2a + z = -7
z = -7 - 2a

then substitute the result (-7 - 2a) into the second equation:

-9a - 6(-7 - 2a) = -2
-9a + (-6 x -7) + (-6 x -2a) = -2
-9a + 42 + 12a = -2
-9a + 12a = -2 - 42
3a = -44
a = \( \frac{-44}{3} \)
a = -14\(\frac{2}{3}\)

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.

9z + 1 < -4 + 6z
9z < -4 + 6z - 1
9z - 6z < -4 - 1
3z < -5
z < \( \frac{-5}{3} \)
z < -1\(\frac{2}{3}\)

The perimeter of a triangle is the sum of the lengths of its sides:

p = x + y + z
p = 15cm + 7cm + 8cm = 30cm

A parallelogram is a quadrilateral with two sets of parallel sides. Opposite sides (a = c, b = d) and angles (red = red, blue = blue) are equal. The area of a parallelogram is base x height and the perimeter is the sum of the lengths of all sides (a + b + c + d).

For parallel lines with a transversal, the following relationships apply:

• angles in the same position on different parallel lines equal each other (a° = w°, b° = x°, c° = z°, d° = y°)
• alternate interior angles are equal (a° = z°, b° = y°, c° = w°, d° = x°)
• 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°)

Applying these relationships starting with a° = 36, the value of z° is 36.