Habakkuk, do you know the order of operations? It's:
In this case, you might be thrown off because parentheses come first, but here, you can't combine the "unlike terms" (3 and -6y). So, you can take it out of the parentheses by distributing the minus sign:
8x - 7y - 3 + 6y (it's like you multiplied both terms inside the parentheses by -1, and since 2 negatives multiplied make a positive product, it's positive 6y)
you can then combine all the y like terms:
y - 3 + 6y
7y - 3
You can't combine the - 3 because it doesn't have a y in it, so that's your final answer (there's no solution for y, that's just the most simplified form).