what percent of the area between f(x)=e^-x2 and the x axis is between x=-2 and x =2
That equals the ratio of the integral of e^-x^2 from 0 to 2 to the integral of e^-x^2 from 0 to infinity. (The curve is symmetric about the y axis, so you only need to do one half of the integration.)
You can find the answer in tables of the probability integral. It is 0.99532