what fraction remains

Question

Scott bought a large bag of cookies at the bakery. He ate 2/7 of a bag and his sister ate 1/6 of a bag, what fraction of the bag remains?

Answer 1

2/7+ 1/6

Find common denominator which is 42

Multiply top and bottom of first fraction by 6 and Multiply top and bottom of second fraction by 7

New fractions are

12/42 + 7/42 = 19/42

Since the bag was 1 whole we need to make that 42/42

42/42 minus what they ate will tell fraction of the bag remains

42/42 - 19/42 = 23/42