Answer:
Last year: 49 students
Step-by-step explanation:
There were 23 more students this year than last year. This means that 72 is equivalent to x, or a random number, plus 23
If 23 + x =72
Then x = 72 - 23
Which means that x = 49, or that the number of students that completed projects for the science fair is 49.
Hope this helps!!!