Solving 2 simultaneous equation

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Find the value of x and y .The complete question can be found below.

Find the value of x and y which satisfy the simultaneous equation if:

8ˣ/128 = 1/4ʸ  
And
49ˣ/7ʸ = 1

so I tried to "eliminate" variable (1) by substituting that variable into (2) with multiplying (1) with 2 and (2) with 3

and I got these (-4y X 14 = 6x) - (3y = 6x) = -7y X (-14-3y) = 0 and y = 0

Can you tell me what is my mistake and how to solve this equation?

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For the second equation you can write $49^x$ as $7^{2x}$, and then $\frac{7^{2x}}{7^y}=1$. Now rewrite this equality as $7^{2x-y}=1$. What should $2x-y$ be equal to so that the equation is solved? You can do the same for the first equation , write everything as a power of $2$ , then you get two equations for $x$ and $y$. I assume you can solve it yourself from here.