With two reapers operating, a field can be harvested in 1 h. If only the newer reaper is used, the crop can be harvested in 1.5 h. How long would it take to harvest the field using only the older reaper?

x  three hours

Step-by-step explanation:

With two reapers a field can be harvested in 1 hour

Operating only the newer reaper  crop can be harvested in 1,5 hour (3/2), then in one hour it does 1/(3/2)  =  2/3

Let call  x number of hours the older reaper, take doing the job, then

In 1 hour time the older reaper does  1 / x

Then according to problem statement

As with  two reapers the field can harvested in one hour

1/ x  + 2/3  = 1    ⇒  ( 3  +  2*x  ) /3*x   =  1

3  +  2*x  = 3*x

- 3*x  + 2*x  = - 3

- x = -3

x = 3