Answer:
[tex]m_2 = 23 kg[/tex]
Explanation:
As we know that the tension in two strings are
[tex]T_2 = 111 N[/tex]
[tex]T_4 = 222 N[/tex]
now we have
[tex]F_{net} = ma[/tex]
so we can say
[tex](m_1 + m_2)a = T_2[/tex]
[tex](12 + m_2)a = 111[/tex]
also we have
[tex](m_1 + m_2 + m_3 + m_4) a = T_4[/tex]
[tex](12 + m_2 + 15 + 20) a = 222[/tex]
now divide two equations
[tex]\frac{222}{111} = \frac{47 + m_2}{12 + m_2}[/tex]
[tex]2m_2 + 24 = 47 + m_2[/tex]
[tex]m_2 = 23 kg[/tex]