The interest earned by the Education Savings Office is tax-free. Dad saved Xiao Xiao's education savings for three years, with an annual interest rate of 5.40%.

The cubic of principal =22646/( 1+5.4%) = 19340.59 yuan.

Bank deposits are calculated according to compound interest, that is, rolling interest. Let the principal be x.

Sum of principal and interest at the end of the first year =X*( 1+5.4%)

Sum of principal and interest at the end of the second year = x * (1+5.4%) * (1+5.4%)

Sum of principal and interest at the end of the third year = x * (1+5.4%) * (1+5.4%) * (1+5.4%) = 22646.

Find x and get 19340.59.