Hi!
Isolate x on one side in either of the equations.
x + 6y - 6y = 15 - 6y
x = 15 - 6y
Now put the value of x in the other equation.
-15 + 6y + 4y = 5
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Simplify
-15 + 10y = 5
Add 15 to both sides
-15 + 15 + 10y = 5 + 15
10y = 20
Divide by 10 on both sides
10y/10 = 20/10
y = 2
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Now put the value of y in to solve for x.
x + 6 * 2 = 15
x + 12 = 15
x + 12 - 12 = 15 - 12
x = 3
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The answer is y = 2 and x = 3
Hope this helps! :)
-Peredhel