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.

4a² - 6a² = -2a²

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.

5b - 7 < \( \frac{b}{-7} \)
-7 x (5b - 7) < b
(-7 x 5b) + (-7 x -7) < b
-35b + 49 < b
-35b + 49 - b < 0
-35b - b < -49
-36b < -49
b < \( \frac{-49}{-36} \)
b < 1\(\frac{13}{36}\)

The first step to solve a quadratic equation that's set to zero is to factor the quadratic equation:

x² + 8x + 16 = 0
(x + 4)(x + 4) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, (x + 4) must equal zero:

If (x + 4) = 0, x must equal -4

So the solution is that x = -4

The sum of the interior angles of a triangle is 180°:
180° = a° + b° + c°
c° = 180° - a° - b°
c° = 180° - 23° - 36° = 121°

A parallelogram is a quadrilateral with two sets of parallel sides. Opposite sides (a = c, b = d) and angles (red = red, blue = blue) are equal. The area of a parallelogram is base x height and the perimeter is the sum of the lengths of all sides (a + b + c + d).