Question

- 4u + 4x = 12 \\ - u = - 2" alt=" - 4u + 4x = 12 \\ - u = - 2" align="absmiddle" class="latex-formula">

Answer 1

When u=-2, put that in where you see "u". use parentheses.
-4(-2)+4x=12

-4*-2=8 ➡positive 8 since a negative times a negative is always positive
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now look for x
8+4x=12
subtract 8 from both sides. get x by itself.

-8+8+4x=12-8
4x=4➡ divide both sides by 4. a number divided by itself is 1 (unless one side is negative, then the answer is negative)
4/4=1
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x=1