For this case we have that by definition, the equation of a line in the slope-intersection form is:

Where:
m: It is the slope
b: It is the cut point with the y axis
The slope is: 
Thus, the equation is of the form:

We substitute the given point and find "b":

Finally, the equation is:

Answer:

X = 4.33333333333
y = 5.33333333333
z = 6.33333333333
UGH I think I did this before but I totally forgot how to do it. Give me a minute to do some research and remember because I'm about 79% sure I know how to do this!
Answer:
x + 3
Step-by-step explanation:
Because he bought an unknown number of soccer balls that is where we use the variable, x. And we know that he bought 3 baseballs, and we add them both to get the total number of things bought. Hope this helped and you could give brainliest :)