book Maths Puzzle Numerical Ability

i need help with this question, i dont understand how to do it.

solve for x in terms of y

x - 2y = 18

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book Other Question

MULTIPLY AND SIMPLIFY

5i(4i-6)
OK I need to simplify this question

x-2 / 3x-2y
*times*
9x^2-4y^2 / 2x^2+x-10

A) 3x-2y / 7x+1
B) 3x+2y / 2x-5
C) 3x+2y / 2x-5
D) 3x^2+2y^2 / 2x+5

Thanks!