294 blue balls, 252 pink balls and 210 yellow balls are distributed equally among some students with none left over. what is the biggest possible number of students?

You have to find the greatest number that divide 294, 252 and 210, i.e., the greatest common factor.

Then, you need to factor each number and calculate the product of the common factors raised to the lowest exponent.

294 = 2*3*7^2
252 = 2^2 * 3^2 * 7
210 = 2*3*5*7

Greatest common factor = 2*3*7 = 42

The biggest possible number of students to distribuute the balls equally is 42

Subtracting is the opposite of adding