book Maths Puzzle Numerical Ability

I am trying to home school my son and I am having difficulty in explaining the steps for this quadratic equation problem in completing the square.
0.4x2 + 1.1 =2
I know that you have to multiply the decimals by 10 to get rid of the decimals.

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book Other Question

The average distance between the earth and the sun is 93 million miles. Using the velocity of light (which is 186000 mi per second) find an approximate value for the amount of tim 1. Use Cramer's Rule to solve for z.

3x+2y-z=17
2x+3y-z=15
2x-3y-z=-3

2. Solve the system:
2x+y+3z=-5
y+z=3
4x+3y+7z=3

3.Find the values of A and B in the following