Answer:
First and second box had 80 and 75 lb flour originally.
Step-by-step explanation:
Let the two boxes contained x lb and y lb of the flour respectively.
Both the boxes contained 155 lb of flour in total.
So the first equation will be,
x + y = 155 --------(1)
If the 20 lb of the flour is taken out then amount of flour in first box = (x - 20) lb
and added to the second box then flour in second box = (y + 20) lb
After the mixing of flour statement says that "the first box will contain of the flour now in the second box."
For this statement equation will be
19(x - 20) = 12(y + 20)
19x - 12y = 380 + 240
19x - 12y = 620 ------(2)
Equation (1) × 12 + equation (2)
12(x + y) + (19x - 12y) = 155×12 + 620
31x = 1860 + 620
31x = 2480
x =
x = 80 lb
from equation (1)
80 + y = 155
y = 155 - 80
y = 75 lb.
Therefore, first and second boxes had 80 lb and 75 lb of flour originally.