Intermediate Algebra (11th edition)

21.For Valentine’s Day, Ms. Sweet will mix
some $2-per-lb nuts with some $1-per-lb
chocolate candy to get 100 lb of mix,
which she will sell at $1.30 per lb. How
many pounds of each should she use?

26. 27.

• 7 x+ 2 y= 17

6 x+ 3 y= 9

4 x- y= 14

2 x+ 5 y=- 4

28. 29.

y- 2 z= 4

3 x+ z= 2

x+ 3 y= 7

• 2 x- y+ z=- 1

3 x+ 4 y+ 2 z=- 2

x+ 2 y- z= 1

MIXED REVIEW EXERCISES

30.Concept Check Which system, A or B, would be easier to solve using the substitu-
tion method? Why?
A. B.
y=- 3 x+ 1

7 x+ 2 y= 4

2 x+ 8 y= 3

5 x- 3 y= 7

Solve by any method.

1

3

x-

2

9

y= 2

2

3

x+

1

6

y=

19

2

33. 34.

• 3 x+ 2 y=- 9

x+ 4 y= 17

2 x+ 3 y= 3

x= 7 y+ 10

35. 36.

3 x+ 4 y= 10

2 x- 5 y= 8

5 x+ 2 y= 8

• 7 x+ 3 y= 12

32.

• 8 x- 20 y+ 4 z= 31
  
  
  • x+ y- 4 z=- 10
  
  
  
  

2 x+ 5 y- z= 12

37.To make a 10% acid solution, Jeffrey Guild wants to mix some 5% solution with 10 L
of 20% solution. How many liters of 5% solution should he use?

38.In the 2010 Winter Olympics, Germany, the United States, and Canada won a com-
bined total of 93 medals. Germany won seven fewer medals than the United States,
while Canada won 11 fewer medals than the United States. How many medals did each
country win? (Source:www.vancouver2010.com/olympic-medals)

CHAPTER 4 Review Exercises 259

22.The sum of the measures of the angles of a triangle is 180°. The largest angle measures
10° less than the sum of the other two. The measure of the middle-sized angle is the aver-
age of the other two. Find the measures of the three angles.

23.Noemi Alfonso-Triana sells real estate. On three recent sales, she made 10% commission,
6% commission, and 5% commission. Her total commissions on these sales were
$17,000, and she sold property worth $280,000. If the 5% sale amounted to the sum of the
other two, what were the three sales prices?

24.How many liters each of 8%, 10%, and 20% hydrogen peroxide should be mixed together
to get 8 L of 12.5% solution if the amount of 8% solution used must be 2 L more than the
amount of 20% solution used?

25.In the great baseball year of 1961, Yankee teammates Mickey Mantle, Roger Maris, and
Yogi Berra combined for 137 home runs. Mantle hit 7 fewer than Maris. Maris hit 39
more than Berra. What were the home run totals for each player? (Source:Neft, David S.,
Richard M. Cohen, and Michael Lo Neft, The Sports Encyclopedia: Baseball 2006.)

4.4 Solve each system of equations by using row operations.

Number of Price per

Pounds Pound Value

Nuts x

Chocolate y

Mixture 100