Need a little help with this one

Landon wrote that 3−2.6=4. which statement about his answer is true?

Three numbers x, y, and z are in the ratio 2: 7: 8. if 12 is subtracted from y, then three numbers form a geometric sequence (in the order x, y–12, z). find x, y, and z. there are 2 sets.

Which expression is a perfect cube? a. x8 b. y24 c. m28 d. x64