Nope. You are not being consistent with significant figures. However many significant figures you choose to report y, 10y will have one less. For this reason 10y - y can never equal 1, which is the result required to "prove" that 0.9999999999999 = 1.
B - A = 10y - y = 9y = 9.999999999999 - 0.9999999999999 = 8.9999999999991 (not 9.00000... as per your calculation)
