The general equation of a plane is ax + by + cz = d, where a, b, c, and d are real numbers and a is nonnegative. find the equation of the plane containing
the points (2, 0, 0), (0, 6, 0), and (0, 0, 5). show each step of your process. then graph the plane.

You'll want to think of this as a problem with 3 equations and 3 unknowns. 
First, rewrite the initial equation by dividing everything by D:

(A/D)x + (B/D)y + (C/D)z = 1
 
To make this easier, you can substitute in new variables: A/D = m, B/D = n, and C/D = o. So:

mx + ny + oz = 1
 
Now, you should put each point into this equation, which will give you 3 new equations:
 
2m + 0 + 0 = 1
0 + 6n + 0 =1
0 + 0 + 5o = 1 

In this case you can solve each directly, otherwise you could use substitution:

m = 1/2, n = 1/6, o = 1/5

Now, put these values in the cleaned up equation:

1/2 x + 1/6 y + 1/5 z = 1
 
This is in standard form, however you can multiply each term by 30 to remove fractions:
 
15x + 5y + 6z = 30.

Looks pretty good to me!