Which numbers are the extremes of the proportion 3/4=6/8

How do i work this problem out using the equation a=pe^rt

Assume that a population of 50 individuals has the following numbers of genotypes for a gene with two alleles, b and b: bb = 30, bb = 10, and bb = 10. calculate the frequencies of the two alleles in the population’s gene pool.

X+y=-4 x-y=2 use elimination with adding and subtraction