12* 15 equals 180, which is the total number of parts. 12*( 1+25%) is equal to 15, which is the number of parts produced every day after improvement. 180/ 15 equals 12 days as the answer.

Equation solution: suppose it actually takes x days.

12 * 15 = 12 *( 1+25%)X

180= 15X

X= 180/ 15

X= 12 A: It took 12 days to actually complete the processing task of this batch of parts.