Let X be a random variable with a Poisson distribution, such that P(X > 2) = 0.3. Find P (X < 2).

Question

The question is:

Let X be a random variable with a Poisson distribution, such that P(X > 2) = 0.3. Find P (X < 2).

So, my workings so far are in line with the answer booklet but then the booklet goes;

$$e^{-\lambda}[1+\lambda + \frac{\lambda^2}{2} ] = 0.7\ gives\ \lambda =1.9138... $$

So I'm just wondering how it got from the first section of the equation (which I got) to finding the value of lambda. Any help would be appreciated.