Solve for y by setting one equation =to X after that you can substitute the equation into the other one let's set the first one in X= FORM
X-7y=10
-2x+14y=-20
Add 7y to both sides of the first equation to let x stand alone
X=7y+10
Now you can substitute x on the second equation
-2 (7y+10)+14y=-20
Distribute
-14y-20+14y=-20
Add and simplify
Us cancel out =0
-20=-20
0=0
They are the same equations you can also divide the second equation by -2 which would make it look like this
X-7y=10
-2 (x-7y=10)
Let me know if I have answered your question
With
explanation; i gotcha
Answer: 
<u>Step-by-step explanation:</u>
(1) (12, 18, 27, ...)
The common ratio is:

The equation is:


The equation is:

1) 2a = 9b ⇒ 2:9
2) a + b = 3b ⇒ a = 2b ⇒ 1:2
Answers: 2:9 and 1:2