A rhombus is a parallelogram with four equal-length sides. A square is a rectangle with four equal-length sides.

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 equal sign and the answer on the other.

-8y + 7 = \( \frac{y}{3} \)
3 x (-8y + 7) = y
(3 x -8y) + (3 x 7) = y
-24y + 21 = y
-24y + 21 - y = 0
-24y - y = -21
-25y = -21
y = \( \frac{-21}{-25} \)
y = \(\frac{21}{25}\)

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

p = x + y + z
p = 9cm + 15cm + 6cm = 30cm

A triangle is a three-sided polygon. It has three interior angles that add up to 180° (a + b + c = 180°). An exterior angle of a triangle is equal to the sum of the two interior angles that are opposite (d = b + c). The perimeter of a triangle is equal to the sum of the lengths of its three sides, the height of a triangle is equal to the length from the base to the opposite vertex (angle) and the area equals one-half triangle base x height: a = ½ base x height.

The first step to solve a quadratic expression that's not set to zero is to solve the equation so that it is set to zero:

y² + 6y - 5 = -y + 3
y² + 6y - 5 - 3 = -y
y² + 6y + y - 8 = 0
y² + 7y - 8 = 0

Next, factor the quadratic equation:

y² + 7y - 8 = 0
(y - 1)(y + 8) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (y - 1) or (y + 8) must equal zero:

If (y - 1) = 0, y must equal 1
If (y + 8) = 0, y must equal -8

So the solution is that y = 1 or -8