If you have a problem like:
4x+2y=20
2x+2y=16
You would subtract
4x-2y=20
-2x+2y=16
You would get the new problum
2x=4
You now want to divide the 2 on both sides to solve for x
x=2
Now that you've solved for X you want to solve for y. So use substitution to solve for y. You would want to substatute the x for the 2 in either of the problums. I'll use the first one.
4(2)+2y=20
You first want to multiply te 4(2) you would get a new problum.
8+2y=20
Now you want to subtract the 8 on both sides.
2y=12
The last step to solve for y is to divide the 2 on both sides.
Y=6
So your answers would be
x=2
y=6
After simplifying, the answer comes to x-y. I Hope this helped :).
In the second quadrant, both cos and tan are negative while only sin is positive.
To find tan, we will use the following property below:

Sec is the reciprocal of cos. If cos is a/b then sec is b/a. Since cos is 2/3 then sec is 3/2

Since tan is negative in the second quadrant. Hence,

Answer
20. B
21. B
22. A
23. C
24. A
25. A
Those should be right? Let me know if you need an explanation.