The ratio is 15 ft:10 in. so you want 1/10 of both. 1/10 of 10 is 1 and 1/10 of 15 is 1.5. One inch on the drawing is 1.5 inches. Now you want to find 1/10 inch as it says, so 0.1 inches: 0.15 feet. You don’t have to complete the problem this way, it’s just how I did it.