Question

resolva as equações  7x-21=0

Answer 1

7x = +21
x = 21/7
x = 3

Answer 2

$7x - 21 = 0 \\ 7x = 21 \\ \\ x = \dfrac{21}{7} \\ \\ \boxed{x = 3} \to \boxed{V=\{3\}}$