Need help solving algebraic word problem

Question

Kentucky Blue Grass seed sells for $5.75/lb.  Tall Fescue seed sells for $4.50/lb.  Nursery sells a mixture of the two kinds for $5.25/lb.  let K represent amount of Kentucky Blue Grass nursery uses in a 5 lb. mixture

 

How much Kentucky Blue Grass does nursery use in 5 lb of mix?.

Answer 1

Let K = lbs. of Kentucky Blue Grass seed.

 

Let F = lbs. of Tall Fescue seed.

 

Then:

1. K + F = 5
2. (5.75)K + (4.5)F = 5(5.25)
3. Solve 1. above for F & substitute this quantity for F in 2. above.
4. Solve the resulting equation for K.