Hi!
Use the distribution property.
4 * 3x = 12x
4 * 5 = 20
4 * -3x = -12x
12x + 20 - 12x = x + 19
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Combine like terms and Simplify
12x - 12x + 20 = x + 19
20 = x + 19
Subtract 19 from both sides
20 - 19 = x + 19 - 19
1 = x
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The answer is x = 1
Hope this helps! :)
-Peredhel