Rambutan = 7 units, mangosteen = 5 units. Rambutan has 60 more, the 2-unit difference.

MangosteenDurianRambutanR − M = 2 units = 60

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

  1. Rambutan − mangosteen → 7 units − 5 units = 2 units → 60
  2. 1 unit → 60 ÷ 2 = 30
  3. Rambutan → 7 units = 7 × 30 = 210

There are 210 rambutan trees.

Check: mangosteen 150, rambutan 210; 210 − 150 = 60. ✓