5 and 6 (5 being the square root of 25 and 6 being the square root of 36, which are the closest perfect squares)
x and y are the packs of organic and inorganic fertilizer, respectively.
pounds of nitrogen added = 2x + 6y = 120
pounds of potassium added = 3x + 2y = 54
eliminate the y terms. subtract the first equation from 3 times the second equation.
9x + 6y = 162
-2x - 6y = -120
------------------
7x = 42
x = 6
y = 18
Answer:
P ( snowboard I ski) = 0.5714
Step-by-step explanation:
Conditional Probability
We use the conditional probability formula to solve this question. It is

In which
P(B|A) is the probability of event B happening, given that A happened.
is the probability of both A and B happening.
P(A) is the probability of A happening.
In this question:
Event A: Ski
Event B: Snowboard.
28 out of 120 students ski:
This means that 
16 out of 120 do both:
This means that 
P ( snowboard I ski)

So
P ( snowboard I ski) = 0.5714