Question 164100
Let x=number of kilos needed of the $4 tea
Then 20-x=number of kilos needed of the $5 tea

Now we know that the value of the tea before it's mixed has to equal the value of the tea after it's mixed, ok?
Value of the tea before it's mixed ($ understood)=4x+5(20-x)
Value of the tea after it's mixed=4.60*20=92
So, our equation to solve is:

4x+5(20-x)=92  get rid of parens (distributive law)
4x+100-5x=92  subtract 100 from each side
4x+100-100-5x=92-100  collect like terms

-x=-8  multiply each side by -1
x=8 kilos---------------------------------amount of $4 tea needed
20-x=20-8=12 kilos---------------------------amount of $5 tea needed
CK
4*8+5*12=4.60*20
32+60=92
92=92

Hope this helps------ptaylor