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.