7. A rectangle is divided into 4 different triangles (as shown in the right figure), the green triangle occupies $15 \%$ of the rectangle's area, and the area of the yellow triangle is 21 square centimeters. What is the area of the rectangle in square centimeters?
7. The area of the rectangle is 60 square centimeters
7.【Solution】The sum of the areas of the yellow triangle and the green triangle is $50 \%$ of the area of the rectangle, and the area of the green triangle accounts for $15 \%$ of the area of the rectangle, so the area of the yellow triangle accounts for $50 \%-15 \%=35 \%$ of the area of the rectangle. Given that the area of the yellow triangle is 21 square centimeters, the area of the rectangle is
$$
21 \div 35 \%=60 \text { (square centimeters) }
$$