exam Maths Puzzle Numerical Ability

I hope this is posted in the correct place. I need some help I do not understand how to do this. Thanks for any help you can give.
solve by elimination process and type an ordered pair.
4x - 9y = 14.5
7y - 2x = -8.5

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exam Other Question

((2x+3)^3)^2 if you were to leave a 15% tip for a meal at a restaurant where the total bill came to $13.80, how much would the tip amount to?