②1840 ÷ (1+15%) = 1600 yuan,1600 yuan < 1680 yuan, (1680-65438.
3.75%, the family did earn, earned 3.75%.
③ Solution: If there are x tons of coal in a small coal pile, there are (24-X) tons of coal in a large coal pile.
Question meaning X+4=( 1- 1/4)(24-X)
X+4= 18-3/4X
X+3/4X= 18-4
7/4X= 14
X=8
24-X= 16
A: Big coal pile 16 tons.
④ There are X people in Class A and 76-x people in Class B..
1/6 * x+ 1/8 *(76-x)= 1 1
1/24*x=3/2
X=36 people
So there are 36 students in Class A and 76-36=40 students in Class B.
Arithmetic solution:
If both classes send 1/6 to attend,
Then a * * * sent 76* 1/6=38/3 people.
It is 38/3- 1 1 more than 1 = 5/3 actually dispatched.
That is to say, 1/6 of class B is 5/3 more than 1/8.
So there are (5/3)/(1/6-1/8) = 40 people in class B.
Class A, 76-40=36 people.
⑤8+6= 14 (ton) indicates how many tons Party A and Party B transport at one time.
146/ 14= 10 (times) The remaining 6 (tons) means that Party A and Party B have 6 tons left after ten times of transportation.
10+1=11(vehicle). The remaining 6 tons can just use an armored vehicle.
So, in the end, Car A has 1 1 car, and Car B has1car.
⑥ Solution: There are x triangles and 40-X rectangles.
3X+(40-X)×4= 145
3X+ 160-4X= 145
-X=(- 15)
X= 15
40- 15=25
A: There are 15 triangles and 25 rectangles.