Answer: C. -3y+14
Step-by-step explanation:

Move 3y to ther right side.

So the answer is C. Because x = -3y+14.
{ solution is attached below}
45 Minutes. Time is like subtraction when you want to figure it out :) Hope this helps~!
Sometimes it will, and sometimes it won't.
I reason as follows:
(21 + x) + (30 + 2x) = 51 + 3x has an 'x' term
(42 + x) + (30 - x) = 72 has no 'x' term.
Repeating; it's .252525252525252525252525