3/4 of a pizza is always the same as 6/8 of a pizza. While 3/4 and 6/8 are equivalent fractions, 3/4 and 6/8 of a pizza could represent different amounts.
3/4 of a pizza is always the same as 6/8 of a pizza
as a counterexample you could draw 2 circles and divide one by 4 and the other by 8. then shade 3 of the circle divided by 4 and shade 6 of the circle divided by 8