The area of a triangle is equal to ½ base x height:

a = ½bh
a = ½ x 3 x 7 = \( \frac{21}{2} \) = 10\(\frac{1}{2}\)

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

a² + 3a - 18 = 0
(a - 3)(a + 6) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (a - 3) or (a + 6) must equal zero:

If (a - 3) = 0, a must equal 3
If (a + 6) = 0, a must equal -6

So the solution is that a = 3 or -6

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.

2a⁴ + 5a⁴ = 7a⁴

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.

y + 8 < \( \frac{y}{6} \)
6 x (y + 8) < y
(6 x y) + (6 x 8) < y
6y + 48 < y
6y + 48 - y < 0
6y - y < -48
5y < -48
y < \( \frac{-48}{5} \)
y < -9\(\frac{3}{5}\)

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° - 61° - 38° = 81°

So, d° = 38° + 81° = 119°

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° - 61° = 119°