Suppose a and b are 3x3 matrices such that |a| = 4 and |b| = -2 |(2a)-1| |at b2|

A good way to think about this is take the phrase "miles in hours" from the question. You are given "530 miles in 10 hours" and what you need to figure out is "X miles in 1 hours." To go from 10 hours to 1 hour, you divide by 10. So you also want to divide miles by 10 to keep everything consistent. 530/10 = 53 miles.