Editors from several publishing houses are here today I know there is ambiguity in this sentence, but I don't know how to correct it

That's a good question. Today we have editors from several publishing houses. This sentence is ambiguous: 1. Today we have editors from several publishing houses. 2. Today we have editors from several publishing houses

It is known that an empty set is really contained in M, m in N, and if x belongs to m, 6-x also belongs to M. then the set M contains at most several elements

M is contained in n,
Moreover, X and 6-x belong to M
x≧0,6-x≥0→0≦x≦6
x=0,1,2,3,4,5,6
6-x=0,1,2,3,4,5,6
Therefore, m contains at most seven elements

The distance between the two places is 300 km. The passenger and freight cars run from the two places at the same time. The freight cars are 60 km / h, the passenger cars are 40 km / h, and the waiting time for the freight cars is 1 hour,
How many hours later will the two cars meet?

Let's meet in X hours
60（x-1）+40x=300
100x=300+60=360 x=3.6
Or: if the truck is 60 km / h, assuming that it has been driving all the time, it is equivalent to 60 km more than they have
（300+60）÷（60+40）=3.6

Simplify the following fraction 1. (A & # 178; + 5ab) / (5b & # 178; + AB) 2. (n & # 178; - 9) / (3n-n & # 178;)

1.（a²+5ab)/(5b²+ab)
=a(a+5b)/b(5b+a)
=a/b
2.(n²-9）/(3n-n²）
=(n+3)(n-3)/-n(n-3)
=-(n+3)/n

Mathematical problems about distance and speed
A car from a to B at the speed of 60km / h. when it reached half of the distance, it was delayed for 15 minutes due to refueling. Later, as the speed increased to 80km / h, it arrived at B at the scheduled time. Ask the distance between a and B

120
Let X be the distance
x/60=0.5x/60+1/4+0.5X/80

Is the proportion equation with unknowns right or wrong

The proportion with unknowns is also an equation. Right

Rockets fly in the atmosphere by reaction force. In space, because space is in a vacuum state, what force does it fly by

The vacuum state can be explained by the principle of momentum. If the system has no external force, momentum is conserved. If the gas is ejected, the momentum of the gas is backward to achieve momentum balance, and the rocket needs to move forward
Modern new technology can also take advantage of the solar wind

Solve an equation and find the value of the unknown
This is a question: 3 (x + 2) - 2 (1-x) = 5 (x-1) and another question: no matter what the value of X is, the equation MX + 6 = 2x-3n always holds. It is better to find the value of M and n. It is better to have a detailed and easy to understand explanation

The first equation doesn't hold, no solution, 4 = 5

After the tire is inflated, the inner tube pressure increases and the friction force increases, which acts as a buffer?

On the contrary, if the tire pressure is too low, the contact area with the ground will increase, which will increase the tire resistance, not conducive to driving performance, especially turning performance, but also increase fuel consumption

Mathematics x + 1 / x = 3, what is the square of X

The solution ∵ x + 1 / x = 3, ∵ (x + 1 / x) = 9, ∵ x + 2 + 1 / x = 9, ∵ x + 1 / x = 7

Editors from several publishing houses are here today I know there is ambiguity in this sentence, but I don't know how to correct it