Calculate and simplify the following expressions involving integers: a) -8 + 6, b) -12 - 20, c) 20 - (-30), d) -9 + (-12), e) 3 - (-8), f) 14 - 28, g) -14 + 26, h) -100 - 200. And simplify: a) 15 + (-

$$-8 + 6 = -2$$

The result is $\boxed{-2}$.

b)

$$-12 - 20 = -32$$

The result is $\boxed{-32}$.

c)

$$20 + 30 = 50$$

The result is $\boxed{50}$.

d)

$$-9 - 12 = -21$$

The result is $\boxed{-21}$.

e)

$$3 + 8 = 11$$

The result is $\boxed{11}$.

f)

$$14 - 28 = -14$$

The result is $\boxed{-14}$.

g)

$$-14 + 26 = 12$$

The result is $\boxed{12}$.

h)

$$-100 - 200 = -300$$

The result is $\boxed{-300}$.

2. Simplify the following:

a)

$$15 - 11 = 4$$

The simplified expression is $\boxed{4}$.

b)

$$-230 - 245 = -475$$

The simplified expression is $\boxed{-475}$.

c)

$$300 + 300 = 600$$

The simplified expression is $\boxed{600}$.

d)

$$1235 - 1100 = 135$$

The simplified expression is $\boxed{135}$.

3. Write down the value of $n$ that makes each of the following true:

a)

$$-12 + 12 = n$$ $$0 = n$$

The value of $n$ is $\boxed{0}$.

b)

$$-10 + n = 6$$ $$n = 6 + 10$$

$$n = 16$$

The value of $n$ is $\boxed{16}$.

c)

$$10 + n = 4$$ $$n = 4 - 10$$

$$n = -6$$

The value of $n$ is $\boxed{-6}$.

d)

$$-8 + 2 = n - 8$$ $$-6 = n - 8$$

$$-6 + 8 = n$$ $$2 = n$$

The value of $n$ is $\boxed{2}$.

e)

$$11 - 15 = -15 + n$$ $$-4 = -15 + n$$

$$-4 + 15 = n$$ $$11 = n$$

The value of $n$ is $\boxed{11}$.

f)

$$-7 - n = -15$$ $$-n = -15 + 7$$ $$-n = -8$$

$$n = 8$$

The value of $n$ is $\boxed{8}$.