One of the dog treats in Shelley’s shop is 8 inches long and 3.2 inches wide. She wants to make a miniature version that has proportional dimensions. If the miniature treat will be 3 inches long, how wide should it be? 1.2 inches 1.8 inches 2.3 inches 3.2 inches

Given:
Original dog treat: 8 inches long, 3.2 inches wide.
Miniature dog treat: 3 inches long, ? wide

We simply do cross multiplication of its proportion:

Length to its width.

Original treat: 8/3.2
Miniature treat: 3/x

8/3.2 = 3/x

Cross multiply:
8 * x = 3.2 * 3
8x = 9.6

Find the value of x
x = 9.6/8
x = 1.2

The width of the miniature dog treat is 1.2 inches.

To check:
original treat: 8/3.2 = 2.5
miniature treat: 3/1.2 = 2.5

or: 
8/3.2 = 3/1.2
8 * 1.2 = 3.2 * 3
9.6 = 9.6