book Maths Puzzle Numerical Ability

I am having a horrible time with fractions- well, I'm having a horrible time all together, but right now it's fractions:
solve for y
x/5 + y/4=1

x/4 - y/9=1

-1/9x + 1/3y=1

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book Other Question

negative 2x divded 3 less than or equal to 6. how do you simplify raticals that have an equationon both sides like

X-3=THE SQUARE ROOT OF 30-2X

AND CAN YOU GIVE ME SOME OTHER EXAMPALES.

THANK YOU,
FROM,
MATH BREAKDOWN