book Maths Puzzle Numerical Ability

i dont know how to do some of these problems

2y-4(y-5)+3(y+11)=6y

and

2x+3y=9

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book Other Question

What is the square root of (4a^2)(4a^2)? this one i have no clue!!
two marbles are drawn without replacement from a box with 3 white, 2 green, 2 red, and 1 blue marble. find the probability that both marbles are white.
thanks, your a great help!!