Task: Question Answering
Input (English): Suppose -5*c + 251 = -2*g, 2*g - 257 = -5*c + 6*g. Suppose 5*f - c = -i, -2*i = -5*f + 2*i + 29. Let k = f + -7. What is the units digit of k?
Output (English): 2