31 people came last year, I know this because I removed 15 from 46 which equals to 31. This can be done in many ways either by subtraction or by finding the value of x. So, we all know that 31+x = 46 to find the value of x we have to add 15. So, 31+15 = 46 therefore the answer is 31 people came last year.
Hope this helps!