Question 978100

Here's the question and part of the solution.

How many ordered pairs (x,y) satisfy this system of equations:
x = 2y + 5
y = (2x-3)(x+9)

Here's part of the solution:
Step 1. Substitute y in the 2nd equation into the first equation to get x = 2((2x-3)(x+9)) + 5

Step 2. The above = 4x^2 + 30x - 54

Step 3. The solution says this can be rewritten as: 4x^2 + 29x -54 = 0. 

Here are my problems: What happened to the 5 on the end of the equation in Step 1? Where did the 29 come from in Step 3? 

Thank you for any help?

Helen
<pre>x = 2y + 5 ----- eq (i)
y = (2x - 3)(x + 9) ----- eq (ii)
x = 2[(2x - 3)(x + 9)] + 5 ------- Substituting (2x - 3)(x + 9) for y in eq (i)
{{{x = 2(2x^2 + 15x - 27) + 5}}}
{{{x = 4x^2 + 30x - 54 + 5}}}
{{{0 = 4x^2 + 30x - x - 49}}}
{{{highlight_green(0 = 4x^2 + 29x - 49)}}}