Question

An equation is shown 5x+3x= 5x + 15/2. What value of 3x makes the equation true?

Answer 1

x= 2.5 or 5/2
5x + 3x -5x = 15/2
=> 3x= 15/2

Answer 2

Note: 3x = 15/2 ;

Divide EACH side of the equation by "3" ;
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3x / 3 = (15/2) / 3 ;

x = (15/2) / (3/1) = 15/2 * 1/3 = (15*1)/(2*3) = 15/6 = (15/3)/(6/3) = 5/2
= 2.5.
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So, the equation is true when x = 2.5 ; and when 3x = 7.5 ;
and when 8x = 20.
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