To find the answer, you have to use the formula to calculate the number of combinations as in this case, the order in which the objects are selected doesn't matter:
nCr=n!/r!(n-r)!
n= number of sample points: 10
r= number of sample points in each combination: 5
10C5= 10!/5!(10-5)!
10C5= 10!/5!*5!
10C5= 252
According to this, the answer is that you have 252 different ways to choose your school lunch.
