SOLUTION: Maria's Coffee Shop makes a blend that is a mixture of two types of coffee. Type A coffee costs Maria 4.30 per pound, and type B coffee costs 5.40 per pound. This month, Maria made

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Question 731340: Maria's Coffee Shop makes a blend that is a mixture of two types of coffee. Type A coffee costs Maria 4.30 per pound, and type B coffee costs 5.40 per pound. This month, Maria made 167 pounds of the blend, for a total cost of 825.90 . How many pounds of type A coffee did she use?
Answer by josgarithmetic(39617) About Me  (Show Source):
You can put this solution on YOUR website!
ASSIGN VARIABLES
L=4.30 dollars per pound, type A
H=5.40 dollars per pound, type B
C=825.90 dollars cost of blend typeA+typeB
u=unknown pounds of type A
v=unknown pounds of type B
M=167 pounds blend typeA+typeB

MAKE SYSTEM OF EQUATIONS
Lu%2BHv=C
u%2Bv=M

SOLVE FOR UNKNOWN VARIABLES
Easiest may be use the material sum equation to get a formula for either u or v and substitute this expression into the cost equation and solve for the other variable; and then use the resulting formula in the material sum equation again to solve for a formula for the first variable. The system is already two equations with two unknowns, and these equations are linear.
Since we are asked to find how much of type A coffee, ...
u%2Bv=M
v=M-u, and then
Lu%2BH%2A%28M-u%29=C
You continue from here.

COMPUTE VALUES FOR UNKNONWS
Substitute the values to find the values for u and v.