问题详情

For every positive 2-digit number, x, with tens digit t and units digit u, let y be the 2-digit number formed by reversing the digits of x. Which of the following expressions is equivalent to x - y ？
A.9(t - u)
B.9(u - t)
C.9t - u
D.9u - t
E.0请帮忙给出正确答案和分析，谢谢！