As the scale factor is 4:1 it means that for each 4inches in scale drawing correspond to 1 inch in the object.
Then, to find the side lengths in the object you multiply the measure of each side in the scale drawing by 1/4:
![\begin{gathered} 10in\cdot(1)/(4)=2.5in \\ \\ 10in\cdot(1)/(4)=2.5in \\ \\ 12in\cdot(1)/(4)=3in \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/rp91rviipxqk3eq5yfnfv7407g0dhit9lq.png)
Then, side a is 2.5 inches, side b is 2.5in and side c is 3inches