Final answer:
The question seems to contain a discrepancy regarding the mass number and neutron count. If we rectify this by assuming the atomic number is 27 (as in cobalt), then an ion with three positive charges would have 24 electrons.
Step-by-step explanation:
The number of electrons in an ion of an element with a mass number of 27 and 40 neutrons, which carries three positive charges. First, we must identify the number of protons in the atom's nucleus, because the mass number equals the number of protons plus the number of neutrons. Since the mass number is 27 and there are 40 neutrons, there must be 27 - 40 = -13 protons, which is not possible, indicating there may be a typo or mistake in the question. However, assuming a typographical error and that the atomic number is actually the intended value, for an ion with three positive charges, to find the number of electrons, we must subtract the charge from the number of protons. If the number of protons (atomic number) were indeed 27 (like in cobalt Co), the number of electrons in the ion would be 27 - 3 = 24 electrons.