Addition Level 13: 3d + 2d (both carry). answer-window addition. 1. Fill hundreds478 + 56Step 1: Fill hundreds478plus564raw windows4 + 0 = 4 then release 4running strip4Hundreds window: 4 + 0 = 4. Hold 4; wait for carry from the next window.2. Fill tensStep 2: Fill tens478plus56412raw windows7 + 5 = 12 then keep 2; carry waitsrunning strip42Tens window: 7 + 5 = 12. Hold raw 12; settle carry later.3. Fill onesStep 3: Fill ones478plus5641214raw windows8 + 6 = 14 then keep 4; carry waitsrunning strip424Ones window: 8 + 6 = 14. Hold raw 14; settle carry later.4. Settle carryStep 4: Settle carryKeep ones; carry moves left.raw windows4 | 12 | 14settled digits5 | 3 | 4answer 534Settle raw 4 | 12 | 14 into 534; keep ones and move carry left.