Answer :

Use the cover up method so cover up 10x so it looks like 5y=15 divide it then you have y so plug it in and solve for x hope this helps
xXxGirxXx
10x - 5y = 15       :Cover up the 10x so -5y is left

-5y = 15              :Then, divide the whole equation by -5

y = -3                 (To figure out x, do the opposite and cover up the -5y)