First, we have to analyze how each number grows (the number of thumbs and the number of sticks for each diagram)
So we can build two equations that give us the number of thumbs and the number of sticks for each diagram, let be n for the number of the diagram, so :
Now we can know the number of thumbs and sticks for any diagram, and we can solve the questions provided, first, let's draw the 4th diagram:
Now
How do I know how many sticks are in the sixth diagram?
sticks= 4(6) = 24
There are 24 sticks in the sixth diagram.
How many thumb tacks are in the seventh diagram?
thumbs= 3(7)+1 = 22
There are 22 thumbs in the seventh diagram.