A red light blinks every 12 seconds and a blue light blinks every 9 seconds. When will both lights blink at the same time?

36

Step-by-step explanation:

We need to find the LCM of the two numbers because we need to know the lowest number that 12 and 9 are both in.

12 * 1 = 12

12 * 2 = 24

12 * 3 = 36

12 * 4 = 48

9 * 1 = 9

9 * 2 = 18

9 * 3 = 27

9 * 4 = 36

We can see that 36 is the lowest number that occurs both in 12 and 9 so the blue and red light will both link at 36 seconds