c) \( x_{1}=-9, x_{2}=2,2 x(x-3)=4(2 x+9) \)

Find \( x \). \( \frac{x-1}{3}=\frac{5}{x}+1 \) A. 6.36 OR -2.36 (B) 6.36 (C) 5.46 OR 2.36 (D) No real roots

Find \( n \), \( 3 n-6=18 n^{2} \) A) 0.654 (B) -0.488 (C) 0.654 OR -0.488 (D) No real roots

3. At a school, \( 40 \% \) of the sikthegrade students said that hip-hop is their favorite kind of music. If 100 sixth-gade students preler hip hop music, how many sixth-grade studer are at the school? Explain or show your reasoning.

42. Julio paid \( 7 \frac{3}{4} \% \) sales tax on an item he bought. He figured that if he had bought the item in a neighboring state where the sales tax is \( 8 \frac{1}{4} \% \), he would have paid \( \$ 75 \) more. What was the cost of the item before tax? (C) \( \$ 15,000.00 \) (IS) \( \$ 3,750.00 \) (C) \( \$ 1,500.00 \) (D) \( \$ 150.00 \) (F) \( \$ 37.50 \)

3.18. Determine el máximo comun divisor de los enteros \( 15,18,24 \) y escríbalo como una combinación lineal de \( 15,18,24 \). 3.19. Sea \( a \in \mathbb{Z}^{+} \)tal que \( \operatorname{mcd}(240, a)=1 \), probar que \( 240 \mid a^{4}-1 \).