Let Kris = 1 unit. Kevin is 3 times as heavy, so Kevin = 3 units.
[[model:questions/solutions/q5155.png]]
• Total units = 1 + 3 = 4 units
• 4 units → \(x\) kg
• 1 unit → \(\frac{x}{4}\) kg
• Kris = 1 unit = \(\frac{x}{4}\) kg
Kris’s mass is \(\frac{x}{4}\) kg.
Check: Kevin = \(3 \times \frac{x}{4} = \frac{3x}{4}\). Total = \(\frac{x}{4} + \frac{3x}{4} = x\). ✓