Resposta :
Explicação:
[tex]\Large \text {$ \sf Fr = m.a \dfrac {} {}$}\\\\\Large \text {$ \sf 126 = m.42 \dfrac {} {}$}\\\Large \text {$ \sf m = \dfrac {126} {42}$}\\\Large \text {$ \sf m = 3 kg \dfrac {} {}$}[/tex]
[tex]\Large \text {$ \sf Fr = m.a \dfrac {} {}$}\\\\\Large \text {$ \sf 126 = m.42 \dfrac {} {}$}\\\Large \text {$ \sf m = \dfrac {126} {42}$}\\\Large \text {$ \sf m = 3 kg \dfrac {} {}$}[/tex]