If 3x+4y=60 and 6x-4y=12, what is the product of x and y?
Pick.
A) 80
B) 54
C) 54
D) 72
E) 12

Rationale: given 3 x + 4 y = 60 - - - eq 1 6 x - 4 y = 12 - - eq 2 sum both eqns we get 9 x = 72 = > x = 8 sum 6 x in eq 2 = > 48 - 4 y = 12 . = > y = 9 now xy = 8 * 9 = 72 option d is correct answer .
Answer: D