Explanation:

- The formula for the area of an equilateral triangle is $(\sqrt{3}/4)\times {\text{side}}^2$.

- If the side increases by 34%, the new side length is $1.34\times \text{original side}$.

- The new area will be $(\sqrt{3}/4)\times (1.34\times \text{original side}{)}^2$.

- This area equals $({1.34}^2\times (\sqrt{3}/4)\times {\text{original side}}^2)$.

- The increase in area is ${1.34}^2-1=0.7956$, or 79.56%.

- Option 2: 79.56% is the correct answer.

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