How many machines, working simultaneously at identical constant rates

1) Say, 3 machine requires x hours to produce 1500 widget, so 5 machine requires x -10. Now since the rate is same: 1500/3x - 1500/5x = 10. One equation, one unknown. 450/x - 300/x = 10, or, 150/x =10. so x =15. Sufficient

2) 10 machine take 1 hour to produce 200 widget. So, 1 machine can produce 20 widgets in 1 hour. In 5 hour 1 machine can produce 100 widget. So, we need 15 machine.

D is the answer.

Statement 2 specifies 10 machines, not 1 machine. 10 machines take an hour longer to make 200 widgets, so 1 machine would take an hour longer to make 20 widgets.

Asked:
How many machines, working simultaneously at identical constant rates, would it take to complete a certain work order of 1,500 widgets within 5 hours?

(1) It would take ten hours longer to complete the 1,500 widget order with three machines than it would take to complete it with five machines.
Let one machine take x hours to complete 1500 widget order
3 machines will take = x/3 hours
5 machines will take = x/5 hours
x/3 = x/5 + 10
x = 75 hours
Number of machines required to complete a certain work order of 1,500 widgets within 5 hours = 75/5 = 15 machines
SUFFICIENT

(2) It takes ten machines an hour longer to complete a 2,000 widget order than it takes them to complete a 1,800 widget order.
Let one machine take x hours to complete 1 widget order
It will take 10 machines to complete 2000 widget order = 2000x/10 = 200x hours
It will take 10 machines to complete 1800 widget order = 1800x/10 = 180x hours
200x - 180x = 1
20x = 1
x = 1/20 hours
Number of machines required to complete a certain work order of 1,500 widgets within 5 hours = 1500x/5 = 500/20 = 25
SUFFICIENT

IMO D