Convert the number three thousand eight hundred and forty-five into symbols. How many groups of ten are in 450? Find the area of a rectangle with length 18 cm and width 7 cm.

Three thousand = 3000
Eight hundred = 800
Forty-five = 45

The number in symbols is $\boxed{\text{3845}}$.

There are $\boxed{\text{45}}$ groups of ten in the number 450.

Area ($A$) = Length ($L$) $\times$ Width ($W$)

The area of the figure is $\boxed{\text{126 cm}^2}$.