An equation like 2x + 3 = 7 is a simple type called a linear equation in one ... There are other types of equations, however, that can have several solutions. ... to solve an equation algebraically and you end up with an obvious identity (like 3 = 3)
Let be the random variable denoting the number of girls that are born. Then has a binomial distribution on babies and probability of getting a girl . The probability we want is