Let x be the number of pounds of the first type ($4.40) of nut, and y be the number of pounds of the other one, then we can set the following system of equations:
Solving the first equation for x we get:
Substituting the above result in the second equation we get:
Substituting y=7 in the third equation on the board we get:
Answer: You will need to add 1.5 pounds of the $4.40 nut and 7 pounds of the other one.