the area of a parallelogram is 12 1/4 cm2 if its height is 1 6/7 cm find its base

Suppose the base be x cm.
Height = $1\frac{6}{7} \mathrm{cm} = \frac{13}{7} \mathrm{cm}$
And area of parallelogram = $\mathrm{base}\times \mathrm{height}$
$$\begin{gathered} \Rightarrow \frac{13}{7}\times x = 12\frac{1}{4} {\mathrm{cm}}^2 \\ \Rightarrow \frac{13x}{7} = \frac{49}{4} \\ \Rightarrow x = \frac{49}{4}\times \frac{7}{13} = \frac{343}{52} = 6\frac{31}{52} \end{gathered}$$
Therefore the base is $6\frac{31}{52} \mathrm{cm}$