The answer is 2(7a+4) because using distributive property 2 times 7a is 14a and 2 times 4 is 8 so it equals 14a+8
we can factor the whole thing:
(2sin(x) -1)(sin(x)+1) = 0.
Therefore, sin(x) = -1 and sin(x) = 1/2.
For the first one x = 3π/2 and the second is π/6 and 5π/6
So 3π/2, π/6 and 5π/6 are the solutions.
I do kind of have a problem with this because it doesn't mention if you should go over 360°. Otherwise, you have to add in an 2nπ into the equations like 3π/2 + 2nπ; 
but I don't know if that is necessary for you.
Ok so for starters you want to choose an equation and solve for a variable.
So, I am going to choose x from the first equation.
Add y to both sides and you get x=11+y
Next, substitute 11+y for x in the other equation so you get...
2(11+y) +10y=-6
Next distribute the 2 throug the 11 and the y
22+2y+10y=-6
12y=-28
y=-28/12
reduce this fraction to make this easier.
y=-7/3
Now plug in why to either of the equations to find x
x-(-7/3)=11
x+7/3=11
x=11-(7/3)
x=(33/3)-(7/3)
x=26/3
so x = 26/3 and y = -7/3
you can also check to see if this is correct by substituting each of these values into the equations.
Lets begin with our y=mx+b, our constant(b) is 800 that she earns as a salary, our x represents the amount she sells, m then represents the commission which is 8.25% so converting that to a decimal and replacing it as m gets us y = 0.0825x+800. Replace $4500 for x and we have y=0.0825(4500)+800 solve and we get $1171.25
