After losing 3 baseball cards, peter gave half of his remaining cards to bobby. if peter gave bobby 9 baseball cards, how many cards did peter start with? linear equation:   1 /2 (x - 3) = 9 bobby claims that peter started with 21 cards. which statements are true about verifying bobby’s claim? check all that apply. 1. substitute 21 for x in the original equation. 2. substitute any number for x in the original equation. 3. bobby’s claim that x = 21 is correct. 4. the result of verifying bobby’s work is 9 = 9. 5. the result of verifying bobby’s work is 21 = 21.