Question

$5x + 9 = 2x + 21$
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Answer 1

Olá!

$5x + 9 = 2x + 21 \\ 5x - 2x = 21 - 9 \\ 3x = 12 \\ x = \frac{12}{3} \\ \boxed{ \bf{x = 4} }$

Espero ter ajudado! :)

Answer 2

5x + 9= 2x + 21

5x - 2x= 21 - 9

3x= 12

x= 12/3

x= 4