Say Louis addresses x envelopes in some amount of time. In that time, Jane, addressing twice as many, will have addressed 2x envelopes. Total, they'll address 240 envelopes. So, we can add the x and 2x to solve for x.
x + 2x = 240
3x = 240
x = 80
If Louis addresses x envelopes and x = 80, Louis will address 80 envelopes. If Jane addresses twice as many, you do 80 * 2, getting 160 envelopes.
