Question 101750
Let x=number of pounds of cashews needed
Value of the cashews=$7x 

Value of the walnuts=$4*10

Value of the final mixture $5.50*(10+x)

Now we know that the value of the nuts before the mixture is equal to the value of the nuts after the mixture.  So we have:
($ are understood)
7x+4*10=5.50*(10+x)  get rid of parens

7x+40=55+5.5x  subtract 40 and also 5.5x from both sides

7x+40-40-5.5x=55-40+5.5x-5.5x  collect like terms

1.5x=15
x=10---------------------------------number of pounds of cashews needed

CK

7*10+4*10=5.5*20
70+40=110
110=110


Hope this helps----ptaylor