Beth needs 1 2/3 cups of sugar to make a cake and 2 1/4 cups to make a pie. how much sugar does she need to make both?

you are adding 1 2/3 + 2 1/4
 first these are mixed fractions lets change them to regular fractions for 1 2/3 take the whole number and multiply by the denominator 3 and add the numerator, then that number over denominator 3 so
 (1 x 3) +2 = 5/3 do that with 2 1/4
  what did you get?

The answer is 9.7 cm