Answer:
All real numbers
Step-by-step explanation:
21 - 7x = 7(3 - x)
21 - 7x = 21 - 7x
Since both sides of the equation are equal, the answer is all real numbers.
This is college? Woah I'm not advanced. Middle school!

Use substitution:


<span>we're going back to substitution:

therefore

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Answer:
-33
it just adding -3
ex: -6+-3= -9
hope this helped
-18 is the fifth one add -3 and its -21 which is the 6th one. then you keep going and get -33.