Question 1188270
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Justin spent 3/10 of his money on 11 packs of cards. He would be able to
buy another 29 such packs of cards with the remaining amount of his 
money and an additional $20.
(a)   What was the price of 1 pack of cards?
(b)   How much money did Justin have at first?
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<pre>
Let x be the amount Justin had at first.


He spent 0.3x to buy 11 packs of cards;  hence, each pack costs  {{{(0.3*x)/11}}}  dollars.


After spending 3/10 of his money, he still have  0.7x of his money remainder.


Next you write the equation as you read the problem


    0.7x + 20 = {{{29*(0.3x/11)}}}.


It is your basic equation to solve and to find x.


To solve it, multiply both sides by 110.  You will get


    77x + 2200 = 29*3x

          2200 = 29*3x - 77x

          2200 =    10x

          x    = 2200/10 = 220  dollars.


So, Justin had 220 dollars, at first.


3/10  of 220  dollars is  3*22 = 66  dollars.


Since Justin bought 11 packs of cards for 66 dollars, each pack of cards costs 66/11 = 6 dollars.
</pre>

Solved.


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So, you can easily solve the problem using only one single equation for one single unknown,

as if you knows NOTHING about systems of equations.