6 one-dollars = $6 15 five-dollars = $75 9 ten-dollars = $90 Add them
all up to get $171, so that is correct. Add the number of one-dollar
bills and the number of ten-dollar bills together. 6 + 9 = 15, which is
the number of five-dollar bills, so that is correct as well. Add all the
numbers of bills together, 6 + 9 + 15 = 15 + 15 = 30.