1) a population of genetically modified
mosquitos doubles every month passing
along a gene which imparts resistance to
malaria. if this population started out with
twenty insects how many are there after
ten months?

This is a linear equation or y=mx+c. Where y is the number of mosquitos at a particular month and x is the number of months. We know the initial population of the mosquitoes is c=20. They population doubles every month so this is the gradient, m=2. Therefore the equation for the growth of the mosquito population is:
y = 2x + 20.

So after x= 10 months the mosquito population will be,
y=2(10)+20= 40.

There will be 40 mosquitoes after ten months.