Ahockey puck with a mass of 0.35 kg slides across the ice after a slap shot toward the goal. if the puck decelerates at 7.8 m/s/s, what is the coefficient of friction between the ice and the puck?

The sliding friction is the net force acting on puck in horizontal direction,
Therefore, from Newton's 2nd law of motion,
f = ma 
f = sliding frictional force = μmg 
μ =coefficient of sliding friction, m = mass of puck, a = deceleration = 7.8 m/s²
∴ μmg = ma
∴ μ = a/g = 7.8/9.8 = 0.795
Therefore, the coefficient of friction is 0.795

The independent variable would be the fertilizer as it is what the dependent variable (the growth of grass) depends on.