if the answer is D. the equation to represent the ages of students is:
n + n+1 + n+2 = 45
it is showing that n is the age of one student and the other student has age one year more than the first one and third students has age of 2 years more than first student and one year greater than the second student. if we solve this equation for the value of n, we get;
3n + 3 = 45
3n = 45 -3
3n = 42
n = 14
so the age of one student is 14, second student 15 and third student 16 years.
and if we add there ages, 14 + 15 + 16 = 45
