Can you take it from there?
No I can't. I either go -2(7y-3x) = 14y+6x and then go 6x(-14y+6x) and multiply that out which is wrong. Or I take the 6x(7y-3x) = 42xy-18x^2 which is wrong again when combined with 14y+6x. So I have no idea lol. Any further help would be great