reserve a, b, c, d, e for Complex;

theorem :: REAL_2'91_2
  a / (3 * b) + a / (3 * b) + a / (3 * b) = a / b
proof
  thus a/(3*b)+a/(3*b)+a/(3*b)=(a+a)/(3*b)+a/(3*b) by Th62
    .=(a+a+a)/(3*b) by Th62
    .=3*a/(3*b)
    .=a/b by Lm10;
end;
