I'll step through #1, you try #2 using the same technique.

Set it up like this:

1/5 times row 1:

-3 times row 1 add to row 2, replace row 2 with the result:

5/7 times row 2:

-1/5 times row 2 add to row 1, replace row 1 with the result:

x=3 and y=-2

See what you have to do?. Whittle away until you get it in what is known as reduced row-echelon form. Your solutions are in the far right column and you have 0's and 1's in the other 2 columns.