Question: extraction and assignment

I will really appreciate some help with assigning solutions of the solve command to names. For example, when I enter the command...

solve( [3x + 9y=10,8x-7y=20],[x,y])

 

I get the following output:

 

[[x=250/93, y=20/93]]

 

How can I extract the solutions and assign them to x and y which I want to use in subsequent calculations such as ...

 

sin(x) + sqrt (y)

 

Thanks in advance !!

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