Take Mr Soh’s $15.50 out of the $90 to find Mr Tan; the extra part is how much more Mr Tan has.
Plain numbers are given; italic underlined numbers are worked out.
Mr Tan has $59 more than Mr Soh.
Check: $74.50 + $15.50 = $90, and $74.50 − $15.50 = $59. ✓