Question 244886
we have the weight of the box which is represented by b.


we have the weight of the nails which is represented by n.


first formula is:


b + 40*n = 175


second formula is:


b + 20*n = 95


in both equations, solve for b.


b + 40*n = 175 becomes b = 175 - 40*n


b + 20*n = 95 becomes b = 95 - 20*n


since they both equal to b, then they are equal to each other so we get:


175 - 40*n = 95 - 20*n


add 40*n to both sides of this equation and subtract 95 from both sides of this equation to get:


175 - 95 = -20*n + 40*n


combine like terms to get:


80 = 20*n


divide both sides of this equation by 20 to get:


n = 4 grams


substitute in your first equation of b + 40*n = 175 to get:


b + 40*4 = 175


subtract 40*4 from both sides of equation and simplify to get:


b = 175 - 160


simplify further to get:


b = 15


use the value of b  = 15 and n = 4 in the second equation to get:


b + 20*n = 95 becomes:


15 + 20*4 = 95 becomes:


15 + 80 = 95 which is true so the values for b and n are good.


You have:


b = 15
n = 4


b + n = 19


Answer to your question is:


the box and one nail weigh 19 grams which is selection D.