Resposta :
[tex]\Large\boxed{\begin{array}{l}\tt a)~\sf 2\cdot x=6\\\sf x=\dfrac{6}{2}\\\sf x=3\\\tt b) ~\sf x+3x=40\\\sf 4x=40\\\sf x=\dfrac{40}{4}\\\sf x=10\end{array}}\blue{\checkmark}[/tex]
[tex]\Large\boxed{\begin{array}{l}\tt a)~\sf 2\cdot x=6\\\sf x=\dfrac{6}{2}\\\sf x=3\\\tt b) ~\sf x+3x=40\\\sf 4x=40\\\sf x=\dfrac{40}{4}\\\sf x=10\end{array}}\blue{\checkmark}[/tex]