It means the silver is 92% pure, i.e. 92% silver and 8% other metals.
10 percent of 920 = 92 10% of 920 = 10% * 920 = 10%/100% * 920 = 92
80% of 920 = 80% * 920 = 0.8 * 920 = 736
920
920
920
920
920 = CMXX
920 = CMXX
0.45
All multiples of 920, beginning with these: 920, 1840, 2760, 3680, 4600 . . .
Oh, dude, you're hitting me with the math questions. Okay, so 920 percent as a decimal is 9.20. It's like moving the decimal point two places to the left because percentages are just fractions out of 100. Easy peasy, right?