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Math application problem! (Need process)!
1, assuming the original time is x hours, there is a delivery length distance of s =15× (x-24/60) =12× (x+15/60).

X=3 hours to solve the equation

Then S=39 kilometers

2. According to the meaning of the question, if the number is x, then 3x-4xx (-x) = 63.

7X=63

X=9

So 3×9-4×(-9)=63.

3、

4. The house price of Lao Zhang's 3rd floor is 4280×( 1+ 18%)×80.

Assuming that you can buy x square meters, it is 4280× (1-10% )× x = 4280× (1+18% )× 80.

The solution is X= 105 square meter.

5.( 1) If you buy 20 tables and m chairs, according to the regulations of Company A (if there are more than 20 tables, you shall pay separately), the payables are:

2 10×20+70×(m-20) yuan

(2) You must buy 20 tables, and the chairs are unknown. Suppose there are m chairs (m & gt=20):

Expenditure on procurement from Company A: 265,438+00× 20+70× (m-20)

Expenditure on purchasing from Company B: (2 10×20+70m)×80%.

If A=B, the solution is m=40.

The situation is: buy 20 tables and 40 chairs.

(3) You must buy 20 tables and 30 chairs, so:

Expenditure on purchasing from Company A: 210× 20+70× (30-20) = 4,900 yuan.

Procurement expenditure of Company B: (2 10×20+70×30)×80%=5040 yuan.

So, go to company A and buy it.