You can begin by writing a ratio
4:10
To get the total students to 100, you must multiply 10 by 10. Therefore multiply 10x10 and 4x10
This gives a
40:100 ratio
That is how many said pizza is their favorite
To find how many did not, subtract 100-40 (total-part). This gives 60. That means 60 students didn’t say pizza is their favorite.
60
Hope this helps