1. Have you written all the questions? If the writing is complete, it should only be expressed by a formula containing unknowns. If the electricity consumption in April is X kWh, and the electricity bill in May is (1+5%)X * 0.4=0.42X 2, and the original price of this suit is X yuan, then according to the meaning of the question, (1-20%)X *0.9=450.

3.55% of cultivated land accounts for 9/ 1 1 of uncultivated land.

4. Let the unknown quantity be x, then (x-45)/x = 20% and x = 56.25.

Let this road be x kilometers long. According to the meaning of the question, 25%X+69=48%X, so X=300.

6. If the distance from A to B is 1, then the original speed of the train can be expressed as 1/25, and the current speed is 1/20, so (1/25)/(/kloc-)

7. If there are X students in the whole school, the number of boys is 56%X and the number of girls is (1-56%) X.

56%X-( 1-56%)X=84，X=700