since the classroom has 17 students and you need to bake 2 muffins for each, therefore:
total muffins needed=2*17=34 muffins
now, you have baked 5 muffins. The remaining number of muffins (x) can be calculated as follows:
x = total number of muffins - already baked
x = 34 - 5 = 29 muffins