First add 10 to both sides of the equal sign so -10+10 and 15-10 -10+10 cancels out so you are left with -2X and 15-10 is gonna be 5
Second ; you’re left with -2X=5
Last your are gonna divide both steps by -2
So you’re gonna have x= -2.5 or -5/2=-2 1/2(simplified)