Average of two means the total is twice the average. With ratio 1 : 3, Alfred = 1 unit and Martin = 3 units, so 4 units in all.

Plain numbers are given; italic underlined numbers are worked out.

1. Total → 2 × $34 = $68
2. 4 units → $68
3. 1 unit (Alfred) → $68 ÷ 4 = $17
4. Martin → 3 × $17 = $51

Alfred had $17 and Martin has $51.

Check: ($17 + $51) ÷ 2 = $34 and 17 : 51 = 1 : 3. ✓