Combine like terms, 2x + -7x = -5x. Now you have -5x + 6 = 21. subtract 6 from both 6 and 21, the 6 cancels out and 21-6=15. You’re left with -5x=15 Divide 5 on both sides, -5 cancels out, and you’re left with x=-3 sorry this was messy and i hope this made sense!
