(1) At the same time of selling books in a bookstore, yiaina book rental business is launched. Each book is rented for no more than 3 days, and the daily rent is a yuan. If the rent exceeds 3 days, an additional B yuan will be charged every day from the fourth day. If a book is rented for 7 days, the rent will be --- yuan (2) , a set of 5 real numbers, please calculate the product of the sum of rational numbers and irrational numbers. (accurate to 0.1) [real numbers are: square of 3, half of root sign, cube of root sign 4, cubic of negative 2 (without brackets), negative root sign 8]  

(1) At the same time of selling books in a bookstore, yiaina book rental business is launched. Each book is rented for no more than 3 days, and the daily rent is a yuan. If the rent exceeds 3 days, an additional B yuan will be charged every day from the fourth day. If a book is rented for 7 days, the rent will be --- yuan (2) , a set of 5 real numbers, please calculate the product of the sum of rational numbers and irrational numbers. (accurate to 0.1) [real numbers are: square of 3, half of root sign, cube of root sign 4, cubic of negative 2 (without brackets), negative root sign 8]  

(1) The rent is 7a + 4B yuan
(2) Rational numbers are: the square of 3, the cube of root 4, and the third power of negative 2 (without brackets); irrational numbers are: half of root 8
[（3^2+(√4)^3）-2^3]×[√(1/2)-√8]=(9+8-8)×(√2/2-2√2)=9×(-3√2/2)=-13.5√2=-19.1

One cubic meter of wood can be used to make 50 desks or 300 legs. There are 5 cubic meters of wood. Please design how much wood can be used to make desks and legs, and how many class chairs can be made?

Set X cubic meters as the desktop
50x = [300 (5-x)] / 4 a table with 4 legs
So x = 3
So three cubic meters for the table top and two cubic meters for the legs

Skillfully using one variable linear equation (24 13:32:38)
The distance between a and B is 6km. Now they are facing each other at the speed of 2.5km/h and 3.5km/h respectively. At the same time, the dog with a runs to B at the speed of 8km / h. After meeting B, they immediately turn to run to a, and then run to B after meeting A. until B and a meet, they ask for the distance of the dog

Dog walking time is the time a and B meet, speed size unchanged, only the direction of change
Find out the time of meeting: T = 6 / (2.5 + 3.5) = 1 (hour)
The distance of the dog: 1 * 8 = 8km

Application of linear equation of one variable (218:59:0)
There are 108 hectares of forest farm and 54 hectares of pasture in a farm. Now to cultivate a kind of fruit tree, a part of the farm needs to be changed into a forest farm to make 20% of the forest farm area of the pasture area. How many hectares of pasture area need to be changed into a forest farm?
There are two pools a and B with a total water storage capacity of 40 tons. If pool a is injecting 4 tons of water and Pool B is discharging 8 tons of water, then the water storage capacity of pool a and Pool B is equal. How many tons of water were stored in the two pools?

54*0.2=10.8