From the figures, notice that the number of dots increases by 7. This give us the following sequence:
[tex]7,14,21,\ldots[/tex]
To obtain the 2nd step, we add one 7 to the first term.
[tex]7+1(7)=7+7=14[/tex]
To obtain the 3rd step, we add two 7s to the first term.
[tex]7+2(7)=7+14=21[/tex]
To obtain the 4th step, we add three 7s to the first term.
[tex]7+3(7)=7+21=28[/tex]
Notice that we multiply the 7 by the difference of the nth step and 1.
Therefore, to find the 27th step, we add 26 7s to the first term.
[tex]7+26(7)=7+182=189[/tex]
Therefore, there must be 189 dots in the 27th step.
