Short answer:
25 inches is the perimeter of the larger rectangle
Long answer:
Imagine that you have a rectangle where every single side is 1 inch long. The total perimeter of the card is 4 inches, 1+1+1+1. The total perimeter is 4 inches.
Now imagine that you have a larger rectangle which is 1.25 times as wide and long as the smaller rectangle. In other words each side of the larger rectangle is 1.5 inches long. The perimeter of the larger card is 1.25+1.25+1.25+1.25. Because each 1 in the original equation was multiplied by 1.25. The perimeter of your larger rectangle is 5 inches.
Turn that into an equation. 5 inches equals 4 inches times 1.25. In other words, (larger rectangle perimeter) equals (smaller rectangle perimeter) times 1.25
Plug in numbers. You get (Larger rectangle perimeter) equals 20×1.25. Solve that and you get 25. 25 is the answer