Problem: Given that the ratio of 3x−43 x-43x−4 to y+15y+15y+15 is constant, and y=3y=3y=3 when x=2x=2x=2, then, when y=12,x\mathrm{y}=12, \mathrm{x}y=12,x equals:
Answer Choices:
A. 18\dfrac{1}{8}81
B. 37\dfrac{3}{7}73
C. 73\dfrac{7}{3}37
D. 72\dfrac{7}{2}27
E. 888 Solution:
3x−4=k(y+15),6−4=k(3+15)3 x-4=k(y+15), 6-4=k(3+15)3x−4=k(y+15),6−4=k(3+15)
∴k=1/9∴3x−4=1/9(12+15)=3,3x=7,x=7/3\therefore k=1 / 9 \quad \therefore 3 x-4=1 / 9(12+15)=3,3 x=7, x=7 / 3∴k=1/9∴3x−4=1/9(12+15)=3,3x=7,x=7/3