You can stuff envelopes twice as fast as your friend. Together, you can stuff 6750 envelopes in 4.5 hours. How long would it take for each of you working alone to complete the job individually?

If you're twice a fast then ... we'll divide 6750 by 3, that equals 2250.

Equation ... y=your friend and you would be 2y cuz you're twice as fast.

y+2y=6750,

3y=6750

y=2250

Your friend stuffed 2250 in 4.5 hrs.

You (twice as fast) stuffed 4500 in 4.5 hrs.

Working alone, your friend can stuff 2250 in 4.5hrs so it would take 13.5hrs to stuff 6750.

Equation ... (6750/2250) x 4.5hrs = 13.5hrs

You can 4500 in 4.5hrs so it would take you 6.75 hrs to stuff 6750.

Equation ... (6750/4500) x 4.5hrs = 6.75 hrs.