How to find the scale factor of two triangles using the sides?

Set up ratios of the corresponding sides of the triangles. For example, the ratio of small to big triangle sides in two triangles is 5/10, 10/20 and 20/40. Divide both numbers in one of the ratios by their highest common factor. This will give you the scale factor of the bigger triangle to the smaller triangle.
I think hope it helps’

Aand b are correctly balanced reactions. they have the same number of atoms in both sides of the reaction