A store manager finds a stack of money totaling $1290--made up of twenties and fifties. There are 42 bills in all. How many twenty dollar bills are there?

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Answer 1 · 2015-10-17T23:10:23

Twenties = 27 bills
Fifties = 15 bills

twenties = a
fifties = b

#20*a+50*b=1290# (1)
#a+b=42# (2)

Multiplying (2) by 20:

#20*a+50*b=1290# (1)
#20a+20b=840# (2)

Subtracting (1) - (2)

#30b=450#

#b=450/30=15# fifties#

#a=42-15=27 twenties#