Man lives = 23\frac{2}{3}32 not live = 13\frac{1}{3}31
P(at least one lives to 80 years) = P(man lives to 80 not woman) + P(woman lives to 80 and not man) + P(both live to 80)
P=(23×25)+(25×13)+(23×35)P = \left( \frac{2}{3} \times \frac{2}{5} \right) + \left( \frac{2}{5} \times \frac{1}{3} \right) + \left( \frac{2}{3} \times \frac{3}{5} \right)P=(32×52)+(52×31)+(32×53)
