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

a = l x w
a = a x b
a = 3 x 1
a = 3

The area of a triangle is equal to ½ base x height:

a = ½bh
a = ½ x 4 x 7 = \( \frac{28}{2} \) = 14

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.

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°).

To solve this equation, isolate the variable for which you are solving (c) on one side of the equation and put everything else on the other side.

-9c - 7z = 3c + 3z + 1
-9c = 3c + 3z + 1 + 7z
-9c - 3c = 3z + 1 + 7z
-12c = 10z + 1
c = \( \frac{10z + 1}{-12} \)
c = \( \frac{10z}{-12} \) + \( \frac{1}{-12} \)
c = -\(\frac{5}{6}\)z - \(\frac{1}{12}\)