Shen picks a rational number. what is true about the opposite of his number?
a. it is to the left of zero on a number line
b. it is the same distance from zero as his original number
c. it is located at zero on the number line
d. it will be farther from zero than his original number

A lot depends upon your interpretation of "opposite."  Do you mean "reciprocal?"

If you give the number a, the reciprocal would be 1/a.  Is that what you mean?

Or do you mean "the number with opposite sign?"  If you give the number b, "the number with opposite sign" would be -b.

Consider both cases.  Choose a rational number (such as 7/8).  Find the reciprocal of this number.  Find the number with opposite sign of this number.

In this problem it decreased 20%