Aldos coffee shop makes a blend that is a mixture of two types of coffee. type a coffee costs aldo $5.80 per pound, and type of b coffee costs $4.65 per pound. this month, aldo made 156 pounds of the blend, for a total cost of $826.60. how many pounds of type b coffee did he use?

Let A represent amount of Type A coffee pounds used. 
Let B represent amount of Type B coffee pounds used

A + B = 156 
B = 156 - A 
A = 156 - B

5.80A + 4.65B = 826.60 
580 (156 - B) + 4.65B - 826.60 = 0 
904.8 - 5.80B + 4.65B - 826.60 = 0
904.8 - 1.15B - 826.60 = 0 
78.2 - 1.15B = 0 
78.2/1.15 = 1.15B/1.15
68 = B
B = 68 pounds of Type B coffee

There's many more steps you can take to check and etc but am too lazy to put down sorry. 

3x+9+4x+x=8x+9that's the answer for your question.