solve by elimination 2x-4y=18,5x+2y=33.

What have you tried so far?

Code:

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2x - 4y = 18
5x + 2y = 33

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What you need to eliminate one of the two variables is the same coefficient (number preceding the variable) in front of one variable.

You have 2x and 5x, so, they are different. How to make them the same? Multiply the first by 5 and the second by 2, giving 10x and 10x. Now they're the same.

Code:

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2x - 4y = 18  => x5  => 10x - 20y = 90
5x + 2y = 33  => x2  => 10x +  4y = 66

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Do you see what I did? While multiplying, I multiplied everything by 5 and 2 respectively. Now, you can subtract one equation from the other to get only one equation with one variable.

Try this, and I'll show you another method.