Refer to figures.
Before looking at the trim sheet, we need to establish:

• Initial TOM index of 50.0 (Indexing the TOM is unusual, normally we see the DOM index as a way to enter the trim sheet)
• The trim sheet shows the aircraft has 132 seats.
• 4 passengers disembark - no need to calculate their mass.
• 500 kg added to cargo 1
• There is no need to calculate the new TOM
• Ignore the already drawn black line on the trim sheet - no relevance to this question

When entering the trim sheet, start at 50.0 from the top - the TOM index.

Go down vertically to Cargo Hold 1. Each diagonal line represents 500 kg. The arrow points left to show the effect on trim when adding mass. Move one line to the left to add the 500 kg

Go down vertically to Cabin OA. We know that these passengers are from row 3. The seat map at the top right of the sheet shows this is in zone OA. To add the mass, follow the arrow to the left, but we are removing the passengers, so go 4/10 to the right. (Each diagonal is 10 passengers - so move 40% of the gap, with a fine pencil!)

Now we have corrected for both passengers and cargo. Simply draw the line vertically up or down to read of the new index value of 48.5