The question is just asking for 90% of 84,000. To do this, you can change 90% into decimal by moving the decimal 2 place over which gives .90
After that, you multiply .90 by 84,000 which is $75,600
Another way to do this is to convert 90% to a fraction. To do that, you would put 90/100 which can simplify to 9/10. Then you would multiply that by 84,000. 1 of the 0's can cancel, so you are left with 9x8,400 which gives the same answer