(1) D is chosen because the equation with unknown numbers is equation B, and the equation with letters is equation. In fact, this is also true because the unknowns are all represented by letters, but generally speaking, equations containing unknowns should be dominated by equations.
(2)c
(3)b
(4) If D loses five games in a row, it is 14-5 = 9. If d loses five games, he won't score until the last nine. If D wins, it is 9-x, so 3(9-x)+x= 19.
(5) an x+x7 1 = 19.
(6) ( 1) (3) (4) (7) (8)
(7) 4(x-3)=28 square meters =2 meters
(8) Let x person 2 (26-x) = 22+x.
The second one on the right.
(2) If we work together for x hours, we can finish the laying task.
186-2× 18 = 18x+ 12x
150=30x
x=5
A: These two people will lie down for five hours.
(3) let the original x yuan
20x × 0.8= 20x-0.32
16x=20x-3.2
4x=3.2
x=0.8
A: Eighty cents per book.