ANSWER: 32 five-dollar bills
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EXPLANATION:
Let x be number of $5 bills
Let y be number of $10 bills
Since we have total of 38 bills, we must have the sum of x and y be 38
x + y = 38 (I)
Since the total amount deposited is $220, we must have the sum of 5x and 10y be 220 (x and y are just the "number of" their respective bills, so we multiply them by their value to get the total value):
5x + 10y = 220 (II)
System of equations:

Divide both sides of equation (II) by 5 so our numbers become smaller

Rearrange (I) to solve for y so that we can substitute into (II)

Substituting this into equation (II) for the y:

We have 32 five-dollar bills
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If we want to finish off the question, use y = 38 - x to figure out number of $10 bills

32 five-dollar bills and 6 ten-dollar bills
21. 1/7 3/8 1/2
23. 3 5/8 3 3/8 3 1/2
25. 1/6 3/4 2/3
Answer:
In the account that paid 6% Susan invest 
In the account that paid 5% Susan invest 
Step-by-step explanation:
we know that
The simple interest formula is equal to
where
I is the Final Interest Value
P is the Principal amount of money to be invested
r is the rate of interest
t is Number of Time Periods
Part a) account that paid 6% simple interest per year
in this problem we have
substitute in the formula above
Part b) account that paid 5% simple interest per year
in this problem we have
substitute in the formula above
we know that

substitute and solve for x




therefore
In the account that paid 6% Susan invest 
In the account that paid 5% Susan invest 
Answer:
+ 6
Step-by-step explanation:
(-2)·(-3) = + 6
(-)·(-) = +