Question 1144252
let f = cost of file, n = cost of notebook, p = cost of pen.


f = n + 1.20
p = 2 * f
f + n + p = 11.60


solve for n to get:
n = f - 1.20


you have:


n = f - 1.2
p = 2 * f


in the equation of f + n + p = 11.60, replace n with f - 1.2 and replace p with 2 * f to get:


f + p + n = 11.60 becomes:
f + 2 * f + f - 1.2 = 11.60
combine like terms to get:
4 * f - 1.2 = 11.60
add 1.2 to both sides of the equation to get:
4 * f = 11.60 + 1.2
combine like terms to get:
4 * f = 12.80
solve for f to get:
f = 12.40 / 4 = 3.2


since n = f - 1.2, then n = 2
since p = 2 * f, then p = 6.4


you have:
f = 3.2, n = 2, p = 6.4


f + p + n becomes 3.2 + 6.4 + 2 = 11.60.
this confirms the solution is correct.


your solution is that the cost of the file is equal to $3.20.