Answer:
[tex]12[/tex] cm
Step-by-step explanation:
If Kelsey knit a total of [tex]6[/tex] cm of scarf over [tex]2[/tex] nights, then we know that she can knit [tex]\frac{6}{2}=3[/tex] cm each night. Therefore, after [tex]4[/tex] nights of knitting, Kelsey would have knit a total of [tex]3*4=12[/tex] cm of scarf in total. Hope this helps!