A right angle measures 90 degrees and is the intersection of two perpendicular lines. In diagrams, a right angle is indicated by a small box completing a square with the perpendicular lines.

The surface area of a cube is (2 x length x width) + (2 x width x height) + (2 x length x height):

sa = 2lw + 2wh + 2lh
sa = (2 x 4 x 3) + (2 x 3 x 3) + (2 x 4 x 3)
sa = (24) + (18) + (24)
sa = 66

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° - 65° - 68° = 47°

So, d° = 68° + 47° = 115°

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° - 65° = 115°

A line on the coordinate grid can be defined by a slope-intercept equation: y = mx + b. For a given value of x, the value of y can be determined given the slope (m) and y-intercept (b) of the line. The slope of a line is change in y over change in x, \({\Delta y \over \Delta x}\), and the y-intercept is the y-coordinate where the line crosses the vertical y-axis.

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.

-6y + 7 < \( \frac{y}{9} \)
9 x (-6y + 7) < y
(9 x -6y) + (9 x 7) < y
-54y + 63 < y
-54y + 63 - y < 0
-54y - y < -63
-55y < -63
y < \( \frac{-63}{-55} \)
y < 1\(\frac{8}{55}\)