ANSWER
3 inches
Step-by-step explanation
Let 'x' be the shortest side of this triangle. We know that the medium side is 7 more than the short side, so this is (x + 7). Also, the longest side is 4 times the short side, so this is 4x.
Knowing that the perimeter - which is the sum of all three sides, is 25 inches, we can write an equation for x,

Add like terms,

Subtract 7 from both sides,

And divide both sides by 6,

Hence, the shortest side of the triangle is 3 inches long.