7. Using M_V=-2.76(logP-1.0)-4.16, the absolute magitudes of the Cepheids in the two galaxies are -5.73 and -6.67 resepctively.
Since m-M=5log(d/10pc), with m=24.5 in both cases, the distance moduli of the two galaxies are m-M = 30.23 and 31.17, giving distances of 11.1 and 17.1 Mpc.