16, because all the other numbers are odd and 16 is even

can be simplified to by adding the 7 and 10 to get

.

cannot be simplified any more by combining like terms.
By distributing the 2b into the parentheses, you can simplify the expression:

Here you can just add:

Thus, the only expression that cannot simplify any more using adding like terms is the second,

.
Answer:
4×30+5×30=120+150=270
Step-by-step explanation:
looking at the last row, we can see that the total number of students will be 4×30+5×30=120+150=270