The second batch of China traditional books

Analysis: Let the second batch of x copies and the first batch of 1. 1x copies be (1.1x-80): (x+80) = 3: 4.

4.4x-320=3x+240

1.4x=560

X=400 copies

So the first batch = 1. 1×400=440, so a ***=400+440=840.

solution method

1, estimation method: an introductory method when you are just learning to solve equations. Estimate the solution of the equation directly, and then substitute it into the original equation for verification.

2. Apply the properties of the equation to solve the equation.

3. Merge similar terms: transform the equation into a monomial.

4. Move terms: move terms containing unknown to the left and constant items to the right.

5. Delete brackets: Use the rule of deleting brackets to delete brackets from the equation.

6. Formula method: There are some equations, and the general forms of solutions have been studied and become fixed formulas, which can be used directly. Generally solvable multivariate higher-order equations have formulas to follow.

7. Function image method: Use the solution of the equation to solve the geometric meaning of the intersection of two or more related function images.