A = nuts of $2/lb
B = nuts of $7/lb
let's say we'll mix "x" lbs of B to get a mixture with A of "y" lbs, therefore

3x-12 is simplified from parenthesis
Answer:
right
Step-by-step explanation:
The box in the lower corner means that the angle is equal to 90 degrees, which means the angle is a right angle
The triangle is a right triangle