A student incorrectly says the solution to the equation +2/3y-1/7y =357 is y = 289. What error did the student make?
A: The student subtracted 1/7 from -2/3
B: The student multiplied 357 by 17/21
C: The student multiplied 357 by 21/17
D: The student added −2/3 to -1/7