Let's use the information given to calculate Akhil's usual speed first.

We know that Akhil takes 30 minutes (0.5 hours) extra to cover a distance of 150 km when he drives 10 km/h slower than his usual speed.

Let "S" be Akhil's usual speed in km/h. So, his slower speed would be (S - 10) km/h.

The time taken to cover a distance is equal to the distance divided by the speed: Time = Distance / Speed

At his usual speed, it takes him: Time at usual speed = 150 km / S hours

At the slower speed, it takes him: Time at slower speed = 150 km / (S - 10) hours

The difference in time between these two scenarios is 0.5 hours (30 minutes): Time at slower speed - Time at usual speed = 0.5 hours

Now, we can set up the equation and solve for S:

(150 km / (S - 10)) - (150 km / S) = 0.5

To solve this equation, we'll first get a common denominator: [150S - 150(S - 10)] / [S(S - 10)] = 0.5

Now, simplify and solve for S: [150S - 150S + 1500] / [S(S - 10)] = 0.5

1500 / [S(S - 10)] = 0.5

Now, cross-multiply: 2 * 1500 = S(S - 10)

3000 = S^2 - 10S

S^2 - 10S - 3000 = 0

Now, we can solve this quadratic equation for S using the quadratic formula:

S = [-(-10) ± √((-10)^2 - 4(1)(-3000))] / (2(1))

S = [10 ± √(100 + 12000)] / 2

S = [10 ± √12100] / 2

S = [10 ± 110] / 2

Now, we have two possible values for S, but we'll take the positive one because speed cannot be negative:

S = (10 + 110) / 2 = 120/2 = 60 km/h

So, Akhil's usual speed is 60 km/h.

Now, we want to find out how much time he will take to drive 90 km when he drives 15 km/h slower than his usual speed, which would be (60 - 15) = 45 km/h.

Time = Distance / Speed Time = 90 km / 45 km/h = 2 hours

Akhil will take 2 hours to drive 90 km when he drives 15 km/h slower than his usual speed.

Let's break down the problem step by step:

1. A can complete the work in 15 days, so his daily work rate is 1/15 of the work per day.
2. B can complete the work in 20 days, so his daily work rate is 1/20 of the work per day.
3. A and B work together for 6 days. In these 6 days, their combined work rate is (1/15 + 1/20) = (4/60 + 3/60) = 7/60 of the work per day.
4. In 6 days, they complete (6 * 7/60) = 42/60 of the work, which simplifies to 7/10 of the work.

Now, let C complete the remaining 3/10 of the work in 6 days. We can calculate C's daily work rate:

C's daily work rate = Work done by C in 6 days / 6 C's daily work rate = (3/10) / 6 C's daily work rate = 1/20 of the work per day.

Now, let's calculate the total amount earned by each worker:

1. A's share: A worked for 6 days at a rate of 1/15 of the work per day, so he completed (6 * 1/15) = 2/5 of the work. A's share of the money is (2/5) * Rs 800 = Rs 320.

2. B's share: B worked for 6 days at a rate of 1/20 of the work per day, so he completed (6 * 1/20) = 3/10 of the work. B's share of the money is (3/10) * Rs 800 = Rs 240.

3. C's share: C worked for 6 days at a rate of 1/20 of the work per day, so he completed (6 * 1/20) = 3/10 of the work. C's share of the money is (3/10) * Rs 800 = Rs 240.

Now, to check if the total amount is correct, you can add up their individual shares:

Rs 320 (A) + Rs 240 (B) + Rs 240 (C) = Rs 800

So, they should divide the money as follows:

• A gets Rs 320.
• B gets Rs 240.
• C gets Rs 240.