The age gap is 76 − 13 = 63 years and never changes. When GM was 8 times, the gap is 7 units.<br><br>[[model:questions/solutions/q4194.png]]<br><br>• Gap → 76 − 13 = 63<br>• When GM = 8 × James: gap = 8u − 1u = 7u → 63<br>• 1u → 63 ÷ 7 = 9 (James's past age)<br>• Years ago → 13 − 9 = 4<br><br>James's grandmother was 8 times as old as him 4 years ago.<br>Check: 4 yrs ago, James 9, GM 72; 72 = 8 × 9; 72 − 9 = 63. ✓