For the mosquito, $P(bite) = P(land)P(bite \vert land) = 0.1$. $X$ is a geometric random variable. $E[X] = 1/p = 10$ and $Var(X) = \frac{1-p}{p^{2}} = 90$.

For the mosquito and tick combined, $P($mosquito or tick$) = 0.1 + 0.1 \times 0.7 - 0.1 \times 0.1 \times 0.7 = 0.163$. This is again a geometric random variable with $E[Y] = 1/0.163$ and $Var(Y) = (1-0.163)/(0.163^{2})$.