exam Maths Puzzle Numerical Ability

I need help with the Echelon Method on this problem
x-y+z=4
x+y+z=10
2x+y-3z=7
I understand the gauss jordan method to solve this but not the echelon?
3 variables throws me o

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exam Other Question

The formula for calculating the amount of money returned for deposit money into a bank account or CD (Certificate of Deposit) is given by the following:
A=P(1+r/n)
A is the amou which parabola touches the x-axis at one point only?

a)y=x^2+8x+16
b)y=x^2-16
c)y=x^2-5x+6
d)y=x^2+4