m1 g l1 + m2gl2 =m3 g l3 + m4gl4
m4 = g(m1l1+m2l2-m3l3) / gl4 =( m1l1+m2l2-m3l3) / l4 = 6 *3 + 151 *1 - 19 *3 /8 = 14 кг
m1 g l1 + m2gl2 =m3 g l3 + m4gl4
m4 = g(m1l1+m2l2-m3l3) / gl4 =( m1l1+m2l2-m3l3) / l4 = 6 *3 + 151 *1 - 19 *3 /8 = 14 кг