Answer:
6
Step-by-step explanation: <u><em>lcf~ the shortest amount it takes us to get to the desired number</em></u>
let's start with 9, we know 9x2=18 so now we go backwards down the number line to see if and of the numbers times another number will equal 18 also
so 8~ we have 8, 16,24~ no 18 so its not 8
now 7~ 7,14,21~no 18 so not 7
6~ 6, 12, 18~yes it took us 3 times to get to 18, but lets see if there is another
5~ 5,10,15,20~no 18 not 5 either
4~ 4,8, 12, 16, 20~ no 18, not 4 either
3~ 3,6,9,12,15,18~ yes but it took us 6 times to get to 18
now 2~ 2,4,6,8,10,12,14,16,18~ yes but it took us 9 times
so the answer would be 6