For some of the more difficult, abstract questions on the ACT Math test, the “real” math that the test takers have in mind can be quite tricky. But for some of these problems, there might be a way to make the rather abstract problem more concrete, and thus easier. That leads us to an important ACT Math strategy: Picking Numbers.

Consider the following difficult problem which has previously appeared on the ACT.

For every positive two-digit number, *x*, with tens digit *t* and units digit *u*, let *y* be the two-digit number formed by reversing the digits of *x*. Which of the following is equivalent to *x – *y?

A. 9(*t – **u*)

B. 9(*u – **t*)

C. 9*t* – *u*

D. 9*u* – *t*

E. 0