Exercise 7 Page 99

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a The price of one pair of sneakers is $80, so if we want 2 pairs we have to pay twice this amount.

80 * 2= 160 If we also buy x pairs of socks at $12 per pair, we will have to add 12x to 160. 160+12x Since we have a $250 gift card we can spend at most $250. 160+12x ≤ 250 Let's solve this inequality for x to find how many pairs of socks we can buy in this situation.

160+12x ≤ 250

SubIneq

LHS-160≤RHS-160

12x≤ 90

DivIneq

.LHS /12.≤.RHS /12.

x≤ 7.5

Since we cannot buy 0.5 pairs of socks and we do not have enough money to buy 8, we can only buy at most 7 pairs of socks. x ≤ 7 Therefore, we cannot buy 8 pairs of socks.

b The variable x is multiplied by 80. Since $80 is the price for a pair of sneakers, this represents the cost for x pairs of sneakers.

80x Also, 60 is added to the above expression. This has to be the amount we pay for socks. We can determine how many pairs of socks we can buy for $60 by dividing it by 12. 60/12=5 The whole expression is less than or equal to 250, because this is the amount of money we have on our gift card. Therefore, this inequality represents the number of pairs of sneakers we can buy when we buy 5 pairs of socks.

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Exercises p.98-99

Exercise 7 Page 99

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