3x + 21 = 3(x + 7) so what you do first is distribute on the left side (meaning you multiply everything in the parentheses by the number on the outside: in this case 3) so: 3x + 21 = 3x + 21 now when it looks like this ☝️ (the same variables and the same coefficient) you can tell it’s all real numbers or infinitely many although you can continue to subtract 3x from each side to get: 21 = 21 (since it’s true it’s all real numbers / infinitely many) hope this helps :)
