6x + 7y =32
-4x +y =24

You need to understand what you need to do.

In substitution, you are required to replace one variable by its equivalent. What I mean by this is:

If you know that x = 'something'
Then, you can replace x in an equation such as x + y = 2, so that it becomes:
'something' + y = 2

A more practical example is this:
x = 2y - 1
x + y = 2

Replace the 'equivalent' of x in the second equation: (2y - 1) + y = 2
Then, you can solve, giving 3y = 3, and y = 1. Replacing the value of y in any equation gives x = 1.

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In elimination, you add or subtract two equations so that one term is eliminated.
I'll take the previous example.

x = 2y - 1
x + y = 2

I will now put all the similar terms one under the other. x's under x's and y's under y's with the remaining numbers on the same side, like this:
x - 2y = -1
x + y = 2

Then, the easiest way to eliminate one of the variables is to subtract one equation from the other.

Code:

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x - 2y = -1
x +  y =  2 -
0 - 3y = -3

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This gives again y = 1, and using this value, we get x = 1.

Can you try this with your problem? Post your answer. :)