Solution: (1), if the buying price is X yuan, the original selling price is X+2 yuan. According to the meaning of the question, (X+2)* 70%= X+ 0.2, X=4, that is, the purchase price of stationery is 4 yuan. (2) If it is sold at the selling price of X, the title means:1500 * (1+40%) * x-1500 =1500 * 20%; If it is X = 6/7, it will be sold at a discount of 6/7. (There may be something wrong with the data in this question) (3), 25,000+25,000 * 3.24% * 3 = 27,430 (yuan), that is, after three years, the principal and interest * * have 27,430 yuan because the interest earned by education savings is not taxed, including: 3,243-3,000/(3,000 * 3). Then the equation is: 3000+3000 * X% * 3 = 3243 (4), and the meaning of the question is: x+x *1.98% *1* (1-20%) =1. exceed