6

6.8 5. By checking work records, a contractor finds that Kenny Dewitt can wire a room addition in 9 hr. It takes Betty Wohnt 7 hr to wire the same room. How long would it take if they worked together?

9. The HP Officejet 4215 All-in-one printer, fax, scanner, and copier can print in black one copy of a company's year-end report in 10 min. the HP Officejet 7410 All-in-one can print the same report in 6 min. How long would it take the two printers, working together, to print one copy of the report?

15. A long distance trucker traveled 120 mi in one direction during a snowstorm. The return trip in rainy weather was accomplished at double the speed and took 3 hr less time. Find the speed going.

Examples was shown as this truck going forward 120 mi, r, t
Coming back 120 mi, 2r, t-3