Question 190502
CORRECTION!

Let x=no of pounds of hamburger that costs 1.60 per pound
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{{{1.60*x+2.10*70=(x+70)*1.70}}}
{{{1.6x+147=1.7x+119}}}
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Subtracting 119 from both sides, we get:
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{{{1.6x+147-119=1.7x+119-119}}}
{{{1.6x+28=1.7x}}}
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Subtracting 1.6x from both sides, we get:
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{{{1.6x-1.6x+28=1.7x-1.6x}}}
{{{28=0.1x}}}
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Dividing both sides by 0.1, we get:
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{{{28/0.1=0.1x/0.1}}}
{{{x=280}}}
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Therefore we must add 280 pounds of hamburger.