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- \( A = \frac{1}{2} \times 10 \times 15 = 5 \times 15 = 75 \) cm².
- If a solution contains 20% salt and you have 500 grams of this solution, how much salt is present?
- Salt amount = 20% of 500 grams = \( 0.20 \times 500 = 100 \) grams.
- Solve for \( y \) in the equation \( 5y - 7 = 3y + 9 \).
- Subtract \( 3y \) from both sides: \( 5y - 3y - 7 = 9 \), simplifying to \( 2y - 7 = 9 \).
- Add 7 to both sides: \( 2y = 16 \).
