First month:
Rachel spent twice as much as elijah. That means Rachel should have 2 units + 39.20 (spent + left) while elijah had 1 unit that month.

Second month:
Elijah spent twice as much as rachel. That means Rachel should have 1 part + 140 (spent + left) while elijah had 2 parts that month.

Now, it is important to notice that 1 unit is not the same as 1 part since elijah could have taken different days to used up the money.

You can have 2 equations out of this:
2 units + 39.20 = 1 part + 140
1 unit = 2 parts

Thus, you can rewrite the first equation as:
4 parts + 39.20 = 1 part + 140

Solve this new equation by drawing a model or moving the numbers. You would get:
3 parts = 140 - 39.20
The hard part is solved and now you can solve the rest.