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).

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

-9a - 4y = -a - 3y + 1
-9a = -a - 3y + 1 + 4y
-9a + a = -3y + 1 + 4y
-8a = y + 1
a = \( \frac{y + 1}{-8} \)
a = \( \frac{y}{-8} \) + \( \frac{1}{-8} \)
a = -\(\frac{1}{8}\)y - \(\frac{1}{8}\)

The sum of the interior angles of a triangle is 180°:
180° = a° + b° + c°
c° = 180° - a° - b°
c° = 180° - 51° - 32° = 97°

To combine like terms, add or subtract the coefficients (the numbers that come before the variables) of terms that have the same variable raised to the same exponent.

6a + 3a = 9a

The area of a trapezoid is one-half the sum of the lengths of the parallel sides multiplied by the height:

a = ½(b + d)(h)
a = ½(4 + 2)(4)
a = ½(6)(4)
a = ½(24) = \( \frac{24}{2} \)
a = 12