There are no algebraic methods of solving a mixed exponential and polynomial equation. The value of x can be found by guessing, or by other means such as trial and error or graphing.
Attached is a graph showing two solutions. x = 4 is the integer solution (2^4 = 4·4). The irrational solution is approximately x ≈ 0.309906932381. That precision is obtained by Newton's method iteration, easily done by a graphing calculator.
The empirical rule says that approximately 68% of any normal distributed data set lies within one standard deviation of the mean.
The same rule states that about 95% lies within two standard deviations of the mean. Using this rule, and the fact that any normal distribution is symmetric about its mean, you have