In questions like these, I like to make a table for the information.
Then you can start adding the information from the question to the table.
62% of the students have school dinners. So 62% of 1200 is 744.
55% of the students are girls. So 55% of 1200 is 660.
45% of the girls have packed lunches. So 45% of 660 is 297.
Fill the table as you go. It should now look like this.
Each row and column has to add up to the total which lets you work out the rest of the information.