In questions like these, I like to make a table for the information.

||Girls|Boys|Total|

|:-|:-|:-|:-|

|Packed||||

|School||||

|Total|||1200|

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.

||Girls|Boys|Total|

|:-|:-|:-|:-|

|Packed||||

|School|297||744|

|Total|660||1200|

Each row and column has to add up to the total which lets you work out the rest of the information.