SOLUTION: I really don't know know if this type of question belongs in this category. BDW, here's my question. Zildijian's friends gave her a gift costing P240 for her sixteenth birthday.

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Question 920010: I really don't know know if this type of question belongs in this category. BDW, here's my question.
Zildijian's friends gave her a gift costing P240 for her sixteenth birthday. If four more friends had contributed, the cost of each would be P3 less. How many friends bought the gift?
Found 2 solutions by ewatrrr, rothauserc:
Answer by ewatrrr(24785) (Show Source):
You can put this solution on YOUR website!
n the number of friends buying the gift
= P3 |Multiplying thru by n(n+4) so as all denominators = 1
240(n+4) - 240n = 3n(n+4)
3n^2 + 12n - 960 = 0
n^2 + 4n - 320 = 0 (Tossing out the negative solution for unit measure)
(n+20)(n-16) = 0
n = 16 friends bought a gift
and...checking
240/16 - 240/20 = P15 - P12 = P3

Answer by rothauserc(4718) (Show Source):
You can put this solution on YOUR website!
let x be the number of friends, y is money contributed by each friend
xy = 240
(x + 4)*(y - 3) = 240
solve first equation for y
y = 240/x
substitute for y in second equation
(x + 4)*(240/x - 3) = 240
(x + 4) * ((240 - 3x) / x) = 240
(-3x^2 + 228x +960)/x = 240 / 1
cross multiply fractions
-3x^2 + 228x +960 = 240x
-3x^2 - 12x + 960 = 0
use qudratic formula to solve for x
x = (12 + 108) / -6 = -20
x = (12 - 108) / -6 = 16
we want the positive value for x, therefore
16 friends bought the gift