Suppose this batch has x parts.

According to the meaning of the question, there is an equation:

( 1/ 12)X:60=3:2

( 1/ 12)X×2=60×3

( 1/6)X= 180

X= 180×6

X= 1080

A: There are 1080 parts in this batch.

Solution 2:

Because the number ratio of A and B is 3: 2.

therefore

B time required to do it alone: b time required to do it alone =3:2.

That is, the time required for B to do it alone = the time required for B to do it alone ×3/2.

B Time required to do it alone = 12×3/2= 18 hours.

The number of parts in this batch * * * = the number completed by Party B per hour × the time required for Party B to complete it alone =60× 18= 1080.