So: 0.85x=4080

x=4800

So the price three months ago was 4800 yuan.

2,8500 * 0.17 =1445 yuan

3. The part to be paid is (2200-2000)*0.05= 10 yuan.

So the actual income is 2200- 10=2 190 yuan.

4. The pre-tax interest is 864/0.8= 1080 yuan.

Suppose that X yuan was saved at that time.

Then x*2.7%*2= 1080.

The solution is x=20000 yuan.

So I saved 20 thousand at that time.

5、

6. 2.52% for one year, 3.06% for two years and 4. 14% for five years.

7、5/8÷[75%- 1 1/ 15÷ 1 1/3*(3/8-37.5%)]

=5/8÷[75%- 1 1/ 15÷ 1 1/3*0]

=5/8÷75%

=5/8*4/3

=5/6