Question

during the winter months, Starbucks has a sale every 4 days and a McCafe has a sale every 5 days. If stores had a sale today, when is the next time both stores will have sales on the same day

Answer 1

Check the picture below.

so we can just look at it as the LCD and 4 and 5 is 20, so they'll have a simultaneous sale every 20 days or every LCD time.