FIRST PARTWe need to find sin α, cos α, and cos β, tan β
α and β is located on third quadrant, sin α, cos α, and sin β, cos β are negative
Determine ratio of ∠α
Use the help of right triangle figure to find the ratio
tan α = 5/12
side in front of the angle/ side adjacent to the angle = 5/12
Draw the figure, see image attached
Using pythagorean theorem, we find the length of the hypotenuse is 13
sin α = side in front of the angle / hypotenuse
sin α = -12/13
cos α = side adjacent to the angle / hypotenuse
cos α = -5/13
Determine ratio of ∠β
sin β = -1/2
sin β = sin 210° (third quadrant)
β = 210°

SECOND PARTSolve the questions
Find sin (α + β)
sin (α + β) = sin α cos β + cos α sin β



Find cos (α - β)
cos (α - β) = cos α cos β + sin α sin β



Find tan (α - β)


Simplify the denominator


Simplify the numerator


Simplify the fraction

To do this, we're going to use the order of operations (PEMDAS):
P - Parentheses
E - Exponents
M - Multiplication
D - Division
A - Addition
S - Subtraction
First let's do parentheses, there isn't anythig in parentheses we need to simplify, so we can skip this step.
Next let's look for exponents. I see we have a
so let's replace that with
:

Now let's look for multiplcation. We know that things that are right next to eachother in parentheses represent multiplcation, so let's simply this more:



And now we're left with a simple problem we know how to solve.
Answer: 
Hope this helps!
2. y=2x+3
When x =0 and y= something, the 'something' is your y-intercept which is b in the y=mx+b formula. Then we look at what is changed in the x and y value to determine the m part. the x increase by 1 and y increase by 2 so the m part is 2.
3. y=-7x
Same as the last one, there is no y-inter this time because the y=0 when x=0/ So the y deceased by 7 each time and x incease by 1 so it is -7 for the m part.
I do it when the numbers are to big but that's me