The distributive property of multiplications states allows you to multiply each term on the parentheses term by the constant outside the parentheses, for example:
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To solve
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You have to multiply each term on the parentheses by 4, that is, multiply 2x by 4 and 3 by 4

And you get that the equivalent expression is 8x+12
To solve
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You have to multiply the three terms inside the parentheses by 6, so that
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The equivalent expression is 6x+6y+6z