Linear equation in one unknown

A 1,260-galloon tank is filled by two pipes in as many as the smaller pipe brings in galloons per minute. How long will it take each pipe to fill the tank if the larger pipe brings in one galloon per minute more than the smaller pipe?

A company has a certain number of machines of equal capacity that produced a total of 180 pieces each working day. If two machines breakdown, the workload of the remaining machines is increased by three pices per day to maintain production. Find the number of machines?