Answer: 2d
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Work Shown:
d = number of days of his vacation
1 day = 1*2 = 2 outfits
2 days = 2*2 = 4 outfits
3 days = 3*2 = 6 outfits
4 days = 4*2 = 8 outfits
5 days = 5*2 = 10 outfits
and so on.
In general we can say,
d days = d*2 = 2d outfits
d is simply a placeholder or a box where we'll place a number inside. For example, if he's on vacation for d = 7 days, then he'll bring 2*d = 2*7 = 14 outfits.
The expression 2*d is the same as 2d. We can leave out the multiplication sign since having a number next to a variable like this implies multiplication.
