It's not about graphics, it's about numbers. 2 and 4, 4 and 8 are twice, and the difference between the upper 2 and 4 is 2, so the upper 4+2=6 and the lower 6*2= 12 of the third one.

Again, next question:

The relationship between 3 and 9, 4 and 12 is 3 times, and the difference between the first 3 and 4 is 1, so the first 3 is 4+ 1=5 and the last 5*3= 15.