SOLUTION: All people in a village were going on a picnic using many vehicles and there were equal No. of people in each of those vehicles. Half way down their trip, 10 vehicles broke down a

Let "n" be the number of people in each of "v" vehicle originally (than "n" is the same for (or "in") each vehicle, 
    according to the condition).

Then the total number of people is v*n, obviously. It is the total number of people in the village.

After 10 vehicles were broken, the number of remaining vehicles became (v-10), carrying (n+1) people in each.

It gives you an equation 

(v-10)*(n+1) = vn.

Open parentheses, collect like terms, cancel like terms, and you will get from it

10v - v = -10.     (1)

It is your first basic equation.


When next 15 vehicle were broken, the number of remaining vehicles became (v-25), carrying (n+3) people in each.

It gives you an equation 

(v-10)*(n+1) = vn.

Open parentheses, collect like terms, cancel like terms, and you will get from it

25n - 3v = -75.     (2)

It is your second basic equation.


Solve the two equations by any method you know. You will get  n = 9 and  v = 100.

So, there were v*n = 100*9 = 900 people in the village.