Machine A:
60 / 10 = 6 - 10 minute segments per hour
7 x 6 = 42 - parts per hour
42 x 12 = 504 - parts made on Monday
Machine B:
60 / 15 = 4 - 15 minute segments per hour
16 x 4 = 64 - parts per hour
64 x 10 = 640 - parts made on Monday
504 + 640 = 1144 - parts made by the two machines on Monday
Hope this helps!! :)