The length of the rectangle was increased by 10%, and the width by 20%, as the percentage of the area of the rectangle increased.

We denote the length of the rectangle through X cm, and the width through Y cm.
Then the area of the original triangle will be equal to: S1 = X * Y cm2.
After increasing the length by 10%, the length of the rectangle will be: (X + 0.1 * X) = 1.1 * X.
After increasing the length by 20%, its width will be equal to: (Y + 0.2 * Y) = 1.2 * Y.
Then the area of the new rectangle will be: S2 = 1.1 * X * 1.2 * Y = 1.32 * X * Y.
Let’s make a proportion and solve it.
S1 – 100%.
S2 – X%.
X = 100 * S2 / S1 = 100 * 1.32 * X * Y / X * Y = 132%.
132% – 100% = 32%.
Answer: The area will increase by 32%