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° - 54° - 46° = 80°

So, d° = 46° + 80° = 126°

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° - 54° = 126°

Perimeter is equal to the sum of the four sides:

p = a + b + c + d
p = 5 + 9 + 3 + 1
p = 18

A rectangle is a parallelogram containing four right angles. Opposite sides (a = c, b = d) are equal and the perimeter is the sum of the lengths of all sides (a + b + c + d) or, comonly, 2 x length x width. The area of a rectangle is length x width. A square is a rectangle with four equal length sides. The perimeter of a square is 4 x length of one side (4s) and the area is the length of one side squared (s²).

The formula for area is πr². Radius is circle \( \frac{diameter}{2} \):

r = \( \frac{d}{2} \)
r = \( \frac{8}{2} \)
r = 4
a = πr²
a = π(4²)
a = 16π

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.

-7y - 1 > \( \frac{y}{7} \)
7 x (-7y - 1) > y
(7 x -7y) + (7 x -1) > y
-49y - 7 > y
-49y - 7 - y > 0
-49y - y > 7
-50y > 7
y > \( \frac{7}{-50} \)
y > -\(\frac{7}{50}\)