How do I solve this For (-x)?

(Do I just make -x equal 1 or 2?) I’m suppose to solve the equation by elimination. (Can someone give me steps to solving it and I’ll try to do it and you guys check my work?)
7x-9y=21
-x-18y=-3

multiply the 1st equation by -2, then add the result to the 2nd equation

... this will eliminate y

solve the subsequent equation for x

I tried doing that but I think I went wrong somewhere because I did

7x-9y=21
-x-18y=-3

-2•7=-14
-2•9=-18
-2•21=-42

14x-18y=-42
-x-18y=-3

And got -x-0y=-3
-x=-45

...I know this is wrong, can someone help me

you lost the minus sign on the 14

you did this ... -2•9=-18
... the 9 was negative
... to give a positive 18 for cancelling with the -18 in the 2nd equation

should end up ... -15x = -45

To solve the given system of equations using elimination, follow these steps:

Step 1: Write down the two equations:
7x - 9y = 21 (Equation 1)
-x - 18y = -3 (Equation 2)

Step 2: Multiply Equation 2 by (-7). This will allow you to eliminate the x term.
-7 * (-x - 18y) = -7 * (-3)
7x + 126y = 21 (New Equation 2)

Step 3: Rewrite the system of equations:
7x - 9y = 21 (Equation 1)
7x + 126y = 21 (New Equation 2)

Step 4: Subtract Equation 1 from Equation 2 to eliminate the x term:
(7x + 126y) - (7x - 9y) = 21 - 21
7x - 7x + 126y + 9y = 0
135y = 0

Step 5: Solve the resulting equation for y:
135y = 0
Divide both sides by 135:
y = 0

Step 6: Substitute the value of y (y = 0) back into one of the original equations (Equation 1) to solve for x:
7x - 9(0) = 21
7x = 21
Divide both sides by 7:
x = 3

Step 7: Check the solution by substituting the values of x and y into the other equation (Equation 2):
-x - 18y = -3
-(3) - 18(0) = -3
-3 = -3

Since both equations hold true when x = 3 and y = 0, the solution to the system of equations is x = 3 and y = 0.