How much more does a lawyer earn in 20 years than a mathematician earns in 40 years?

20 miles.

Step-by-step explanation:

Let m be the miles traveled by the both Taxi.

Pick up charge of A-1  taxi = $12

Cost of travelling 1 mile = $0.15

Cost of travelling x mile = $0.15x

So, total cost of A-1 taxi =  --A

Pick up charge of Z-6  taxi = $10

Cost of travelling 1 mile = $0.25

Cost of travelling x mile = $0.25x

So, total cost of Z-6 taxi =  --B

Now we are supposed to find At what mileage is the cost for both taxi services the same.

So, equate 1 and 2

So, the cost for both taxi services will be same at 20 miles.