Question

There are a total of 66 students in the

fourth grade at North Elementary
school. Class A has five more
students than Class B. Class C has 2
less students than Class B. How
many students are in class A?

Answer 1

A = 26

Explanation:

sum of students = classA + classB + classC

let's say classA = A, classB = B, and classC = C

A + B + C = 66

class A has five more students than class B, so A = 5 more than B so A = 5+B

class C has 2 less students than class B, so C = 2 less than class B = B -2, so C = B-2

A + B + C = 66

A = 5+B

C = B-2

substitute 5+B for A and B-2 for C in the first equation to limit this to one variable (B)

(5+B) + B + (B-2) = 66

3B + 3 = 66

subtract 3 from both sides to isolate the variable and its coefficient

3B = 63

divide both sides by 3 to solve for B
B = 21

A = 5 + B = 5 + 21 = 26